user111: According to Abhidhamma, the smallest unit of Rupa is called the Suddhashtaka(Pure Octad) which has the following 8 elements:
patavi, apo, tejo, vayo, vanna, gandha, rasa, and oja
Regarding Sunlight, the tejo(heat) and the vanna(color) elements seem obvious, but how does one understand others? 
From a Vipassana point of view, is this problem occurring because the mind is getting stuck at the concept of Sunlight?

user5779: Buddhism focuses on spiritual development, so the Buddhist analysis of rūpa focuses on sense objects, the sense organs and the body. Non-living things are made up of temperature-born pure-octad groups or temperature-born sound groups. The relevance of non-living things in the Buddhist analysis of rūpa is that non-living things are sense objects.
I would say that sunlight itself does not impact the sense directly, only indirectly. When sunlight bounces off a speck of dust or a wall, then we “perceive” the sunlight through the eye sense. When sunlight makes our skin warm or a rock warm, we “perceive” sunlight through the tactile sense.
The speck of dust, the wall, the skin and the rock… all of these are “non-living things” and are temperature-born pure-octad groups (the eight rūpa that you listed above). They are all to be understood as sense objects. 
Using fire-element (tejo) as one example, some sense objects have greater intensity of the fire-element and will be “warmer” to the tactile sense than other sense objects with less intensity of the fire-element, but all sense objects include the fire-element rūpa. The other seven rūpa in the temperature-born pure-octad group can be seen in a similar way... always present, but with different intensities.

user43: According to Vasubandhu's Abhidharma-kosa:

Visible matter (rupa) is twofold.  

Visible matter is color and shape. Color is fourfold: blue, red,
  yellow, white; other colors proceed from out of these four colors. Shape is eightfold: long, short, square, round, high, low, even, uneven.  

Or twentyfold.

Or there are some twenty types: the four primary colors, the
  eight shapes, and eight more colors: cloud, smoke, dust, mist, shade,
  heat, light, darkness. Some make a color of the firmament [which
  appears like a wall of lapiz-lazuli]; this would give us the number
  twenty-one.  
"Even" signifies "of even shape;" "uneven" is the opposite; mist is
  the vapor which rises from the ground and from water; "heat" is
  the light of the sun; "light" is the light of the moon, the stars, fire,
  grasses and gems; "shade"—arisen from an obstacle to light—is where
  forms still remain visible; "darkness" is the opposite. The other terms do not call for any explanation.  
Visible matter (rupa) can be color without being shape:
  blue, red, yellow, white, shade, heat, light, darkness.  
There can be shapes without there being color: that part of the
  long, of the short, etc., which constitutes bodily action.  
There can be color and shape at one and the same time: all the
  other categories of visible matter.
Some other Masters maintain that only heat and light are
  exclusively color; for blue, red, etc., present themselves to the sight
  under the aspect of long, short, etc.


From this you can see that according to Abhidharma of Vaibhasika school which is what Mahayana follows, sunlight can be pure color without shape. As Jayarava used to be fond of repeating (and as Thanissaro Bhikkhu is equally fond of hammering in), the perspective of Buddhism is that of phenomenology and not of metaphysics. From phenomenological standpoint there is absolutely no problem with having a perception of color without a perception of shape (nor taste, smell, nutriment, solidity, adhesion, and motion).

111: <p>According to Abhidhamma, the smallest unit of Rupa is called the <a href="http://www.accesstoinsight.org/lib/authors/mendis/wheel322.html#ruupa" rel="nofollow">Suddhashtaka(Pure Octad)</a> which has the following 8 elements:</p>

<p>patavi, apo, tejo, vayo, vanna, gandha, rasa, and oja</p>

<p>Regarding Sunlight, the tejo(heat) and the vanna(color) elements seem obvious, but how does one understand others? </p>

<p>From a Vipassana point of view, is this problem occurring because the mind is getting stuck at the concept of Sunlight?</p>
 5779: <p>Buddhism focuses on spiritual development, so the Buddhist analysis of <em>rūpa</em> focuses on sense objects, the sense organs and the body. Non-living things are made up of temperature-born pure-octad groups or temperature-born sound groups. The relevance of non-living things in the Buddhist analysis of <em>rūpa</em> is that non-living things are sense objects.</p>

<p>I would say that sunlight itself does not impact the sense directly, only indirectly. When sunlight bounces off a speck of dust or a wall, then we “perceive” the sunlight through the eye sense. When sunlight makes our skin warm or a rock warm, we “perceive” sunlight through the tactile sense.</p>

<p>The speck of dust, the wall, the skin and the rock… all of these are “non-living things” and are temperature-born pure-octad groups (the eight <em>rūpa</em> that you listed above). They are all to be understood as sense objects. </p>

<p>Using fire-element (<em>tejo</em>) as one example, some sense objects have greater intensity of the fire-element and will be “warmer” to the tactile sense than other sense objects with less intensity of the fire-element, but all sense objects include the fire-element <em>rūpa</em>. The other seven <em>rūpa</em> in the temperature-born pure-octad group can be seen in a similar way... always present, but with different intensities.</p>
 43: <p>According to <a href="https://en.wikipedia.org/wiki/Abhidharma-kosa" rel="nofollow">Vasubandhu's Abhidharma-kosa</a>:</p>

<blockquote>
  <p>Visible matter (<em>rupa</em>) is twofold.  </p>
  
  <ol>
  <li>Visible matter is color and shape. Color is fourfold: blue, red,
  yellow, white; other colors proceed from out of these four colors. Shape is eightfold: long, short, square, round, high, low, even, uneven.  </li>
  </ol>
  
  <p>Or twentyfold.</p>
  
  <ol start="2">
  <li><p>Or there are some twenty types: the four primary colors, the
  eight shapes, and eight more colors: cloud, smoke, dust, mist, shade,
  <strong>heat, light,</strong> darkness. Some make a color of the firmament [which
  appears like a wall of lapiz-lazuli]; this would give us the number
  twenty-one.  </p>
  
  <p>"Even" signifies "of even shape;" "uneven" is the opposite; mist is
  the vapor which rises from the ground and from water; <strong>"heat" is
  the light of the sun; "light" is the light of the moon, the stars, fire,
  grasses and gems;</strong> "shade"—arisen from an obstacle to light—is where
  forms still remain visible; "darkness" is the opposite. The other terms do not call for any explanation.  </p></li>
  <li><p><strong>Visible matter (<em>rupa</em>) can be color without being shape:</strong>
  blue, red, yellow, white, shade, <strong>heat, light</strong>, darkness.  </p>
  
  <p>There can be shapes without there being color: that part of the
  long, of the short, etc., which constitutes bodily action.  </p>
  
  <p>There can be color and shape at one and the same time: all the
  other categories of visible matter.</p>
  
  <p>Some other Masters maintain that only <strong>heat and light are
  exclusively color</strong>; for blue, red, etc., present themselves to the sight
  under the aspect of long, short, etc.</p></li>
  </ol>
</blockquote>

<p>From this you can see that according to Abhidharma of Vaibhasika school which is what Mahayana follows, sunlight <em>can</em> be pure color without shape. As Jayarava used to be fond of repeating (and as Thanissaro Bhikkhu is equally fond of hammering in), the perspective of Buddhism is that of phenomenology and not of metaphysics. From phenomenological standpoint there is absolutely no problem with having a perception of color without a perception of shape (nor taste, smell, nutriment, solidity, adhesion, and motion).</p>
