While the first posted answer appears to be a correct solution, their seems to be another possible solution that I wanted to share:
I am described by temperature, and never by looks.
Sunlight is described as warm and all starlight properties are based on temperature, but cannot itself technically be seen by form to be described
I might be found in your camera, as well as children's books.
Sunlight can be seen in lens flares in cameras and illustrated children’s books sometimes depict rays of sunlight
I described what you observed, but perhaps not at night.
Sunlight “describes” (i.e. delineates) what is observed during the day, but not at night (except perhaps when reflected from a visible moon).
I am swallowed by darkness, but am an offspring of light.
No sunlight is present in darkness, but sunlight is a species of the family of light
I have a pair of spellings, with and without;
Sunlight/Sunshine or Sunlight/Starlight (depending on whether one wanted to emphasize the light only from the Earth's Sun, or light from any "suns" out there in space.
An infinitude of relatives, though every eye has its doubt.
Sunlight (from Earth’s Sun) is related to all starlight from the infinitude of the stars, though every person doubts an infinite number of stars exist
All of us can be found where seven rule the family.
There are currently seven defined spectral classes of stars that are related to their light’s temperature
I have not seen it, but there is a pot of gold, apparently.
Sunlight causes rainbows, at the “end” of which is supposedly a pot of gold
My gender is defined by my shade and/or tone.
Light directly from the sun versus reflected sunlight from the moon differs in shade and tone, and the properties of that light have caused cultures to refer to its emitter or reflector by masculine or feminine pronouns (though opinions on which is which vary)
Unravel these clues, and the answer you will own.
I can be light or dark and might be found on a wheel.
Most stars release sun/starlight, but dark stars (theoretcially) do not let the light out, so the light is dark; sunlight is found on sundials.
I am, quite literally, what your eyes may reveal.
Eyes are needed for light of any kind to be revealed (experienced visually).