1. A computer implemented method for evaluating a condition of an ocular surface based on a color of the ocular surface, the method comprising: obtaining a digital image of at least a portion of the ocular surface; receiving a selection of a portion of the image as an evaluation area; for each of a plurality of pixels within the evaluation area: determining a plurality of color components that are based on a Cartesian color space, determining, from the color components, a hue value in a polar coordinate based hue-saturation-value (HSV) color space, selecting an angle range in accordance with a color associated with the ocular condition being evaluated, determining that the hue value lies within the angle range that represents the color associated with the condition being evaluated in a hue circle representation of the HSV color space, mapping the hue value to a scalar value within a predetermined range, in response to determining that the hue value lies within the angle range, selecting a function of one or both of the saturation and value components of the HSV color space, wherein the function is selected based on the condition being evaluated, and determining a color value as a product of the scalar value and the function of one or both of the saturation and value components of the HSV color space; and generating a color score for the evaluation area based on an average of the color values of the plurality of pixels, wherein the color score of the ocular surface relates to a quantitative evaluation of the condition of the ocular surface.