The snowy owl, of course, is mostly white.
They are purer white than predatory mammals like polar bears (Ursus maritimus) and Arctic fox (Vulpes lagopus).
Often when seen in the field, these owls can resemble a pale rock or a lump of snow on the ground.
It usually appears to lack ear tufts but very short (and probably vestigial) tufts can be erected in some situations, perhaps most frequently by the female when she is sitting on the nest.
The ear tufts measure about 20 to 25 mm (0.79 to 0.98 in) and consist of about 10 small feathers.
The snowy owl has bright yellow eyes.
The head is relatively small and, even for the relatively simply adapted hearing mechanism of a Bubo owl, the facial disc is shallow and the ear is uncomplicated.
1 male had ear slits of merely 21 mm × 14 mm (0.83 in × 0.55 in) on left and 21 mm × 14.5 mm (0.83 in × 0.57 in) on the right.
Females are almost invariably more duskily patterned than like-age males.
In mature males, the upper parts are plain white with usually a few dark spots on the miniature ear-tufts, about the head and the tips of some primaries and secondaries whilst the underside is often pure white.
Despite their reputation for being purely white, only 3 out of 129 Russian museum specimens of adult males showed an almost complete absence of darker spots.
The adult female is usually considerably more spotted and often slightly barred with dark brown on the crown and the underparts.
Her flight and tail feathers are faintly barred brown while the underparts are white in base color with brown spotting and barring on the flanks and upper breast.
 In confusingly plumaged snowy owls, the sex can be determined by the shape of wing markings, which manifest as bars more so in females and spots in males.
However, the very darkest males and the lightest females are nearly indistinguishable by plumage.
On rare occasion, a female can appear almost pure white, as has been recorded in both the field and in captivity.
There is some evidence that some of the species grow paler with age after maturity.
One study's conclusions were that males were usually but not always lighter and that correctly aging is extremely difficult, sometimes individuals either get lighter, darker or do not change their appearance with age.
On the other hand, with close study, it is possible to visually identify even identify individual snowy owls using the pattern of markings on the wing, which can be somewhat unique in each individual.
After a fresh moult, some adult females that previously appeared relatively pale newly evidenced dark, heavy markings.
On the contrary, some banded individuals over at least four years were observed to have been almost entirely unchanged in the extent of their markings.
In another very pale owl, the barn owl (Tyto alba), the sexual dimorphism of spotting appears to be driven by genetics while, in snowy owls, environment may be the dictating factor instead.

The chicks are initially grayish white but quickly transition to dark gray-brown in the mesoptile plumage.
This type of plumage camouflages effectively against the variously colored lichens that dot the tundra ground.
This is gradually replaced by plumage showing dark barring on white.
At the point of fledging, the plumage often becomes irregularly mottled or blotched with dark and is mostly solidly dark gray-brown above with white eyebrows and other areas of the face white.
Recently fledged young can already be sexed to a semi-reliable degree by the dark marking patterns about their wings.
The juvenile plumage resembles that of adult females but averages slightly darker on average.
By their second moult fewer or more broken bars are usually evidenced on the wing.
The extent of white and composition of wing patterns become more dimorphic by sex with each juvenile moult, culminating in the 4th or 5th pre-basic moult, wherein the owls are hard to distinguish from mature adults.
Moults usually occur from July and September, non-breeding birds moulting later and more extensively, and are never extensive enough to render the owls flightless.
Evid
The snowy owl, of course, is mostly white. They are purer white than predatory mammals like polar bears (Ursus maritimus) and Arctic fox (Vulpes lagopus). Often when seen in the field, these owls can resemble a pale rock or a lump of snow on the ground. It usually appears to lack ear tufts but very short (and probably vestigial) tufts can be erected in some situations, perhaps most frequently by the female when she is sitting on the nest. The ear tufts measure about 20 to 25 mm (0.79 to 0.98 in) and consist of about 10 small feathers. The snowy owl has bright yellow eyes. The head is relatively small and, even for the relatively simply adapted hearing mechanism of a Bubo owl, the facial disc is shallow and the ear is uncomplicated. 1 male had ear slits of merely 21 mm × 14 mm (0.83 in × 0.55 in) on left and 21 mm × 14.5 mm (0.83 in × 0.57 in) on the right. Females are almost invariably more duskily patterned than like-age males. In mature males, the upper parts are plain white with usually a few dark spots on the miniature ear-tufts, about the head and the tips of some primaries and secondaries whilst the underside is often pure white. Despite their reputation for being purely white, only 3 out of 129 Russian museum specimens of adult males showed an almost complete absence of darker spots. The adult female is usually considerably more spotted and often slightly barred with dark brown on the crown and the underparts. Her flight and tail feathers are faintly barred brown while the underparts are white in base color with brown spotting and barring on the flanks and upper breast.  In confusingly plumaged snowy owls, the sex can be determined by the shape of wing markings, which manifest as bars more so in females and spots in males. However, the very darkest males and the lightest females are nearly indistinguishable by plumage. On rare occasion, a female can appear almost pure white, as has been recorded in both the field and in captivity. There is some evidence that some of the species grow paler with age after maturity. One study's conclusions were that males were usually but not always lighter and that correctly aging is extremely difficult, sometimes individuals either get lighter, darker or do not change their appearance with age. On the other hand, with close study, it is possible to visually identify even identify individual snowy owls using the pattern of markings on the wing, which can be somewhat unique in each individual. After a fresh moult, some adult females that previously appeared relatively pale newly evidenced dark, heavy markings. On the contrary, some banded individuals over at least four years were observed to have been almost entirely unchanged in the extent of their markings. In another very pale owl, the barn owl (Tyto alba), the sexual dimorphism of spotting appears to be driven by genetics while, in snowy owls, environment may be the dictating factor instead. 
The chicks are initially grayish white but quickly transition to dark gray-brown in the mesoptile plumage. This type of plumage camouflages effectively against the variously colored lichens that dot the tundra ground. This is gradually replaced by plumage showing dark barring on white. At the point of fledging, the plumage often becomes irregularly mottled or blotched with dark and is mostly solidly dark gray-brown above with white eyebrows and other areas of the face white. Recently fledged young can already be sexed to a semi-reliable degree by the dark marking patterns about their wings. The juvenile plumage resembles that of adult females but averages slightly darker on average. By their second moult fewer or more broken bars are usually evidenced on the wing. The extent of white and composition of wing patterns become more dimorphic by sex with each juvenile moult, culminating in the 4th or 5th pre-basic moult, wherein the owls are hard to distinguish from mature adults. Moults usually occur from July and September, non-breeding birds moulting later and more extensively, and are never extensive enough to render the owls flightless. Evid
Snowy owl