This right here is what I was looking for!
If you need ideas it would work similar to a glowstick or the Tropical crystal dragons from ark. The gene glows in the color of the marking slot, could be brighter or softer in places. Could work as a secondry gene as well.
Primary gene: Luminous
What it does: The body seems to glow in whatever color is assigned to that slot, brighter around the face, limbs, spike and tail. being softer or duller in other areas.
Secondary Gene: Neon or Glowstick
What it Does: Lights up the wing membranes with whatever color is assigned to the wings, similar to the body, being brighter at the elbow (or the edges) getting softer as it travels away from that location.
Tertiary Gene: (whatever one was NOT used above or something equally fitting)
What It does: I feel like a smoky version of a swirl or something like clouded "spots" on the top half of the body (midway line up) in the color assigned to that slot, the gene would shimmer and glow like an aurora borealis, taking on not just the tertiary color but perhaps the primary and secondary colors as well?
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In other news what about a cake gene.
Primary Gene: Cake
What it looks like: well the body would take on a spongy texture, with 1-3 thin layer like strips of "frosting" in the same color as the tertiary gene slot.
Secondary Gene Sponge? (i was thinking of the texture and of sponge cake)
would be similar but on the wings, maybe with more or less holes.
Tertiary gene Frosting
would start at the top of the dragon and "melt" down the side of the body in a very uneven fashion (like cream cheese frosting on warm cake) in the color of the assigned marking slot, with (or without) sprinkles in the same color as the eyes! (Hearts for girls | Stars for boys or a mix of both cause why not)
Alternative Tertiary gene: Gingerbread
basically what you would expect to see on a frosted gingerbread dragon cookie.