Eyes are highly customizable! The import comes with two pupil options, Slit and Round, a Shading layer, a Shine layer, and a layer to place your chosen eye color. The shade/shine options are optional and may be redrawn, and the pupil may be redrawn to be slit, oval, or round, or to resemble a real life reptile's eyes. The iris itself may be redrawn, as long as some of the sclera (white) is easily visible.
Eye color can be solid, a two color gradient, two color central heterochromia, or full heterochromia. Partial heterochromia is currently reserved for markings affecting the skin around the eyes. Shading or effects can make this look more dramatic, but two easily distinguishable colors (such as red and blue) may be used. If two adjacent colors are used (like blue and green), the eye may gradient through a third in between color (like teal). Eyes may be dark, almost black, but the pupil should always be darker than the iris. The pupil may be colored, but must be about in the Off-Black slider's range. The eye cannot glow unless the dergon has an Arcane or Radioactive gene.
The sclera must remain a color in the White or Off-White slider, unless affected by an Arcane or Radioactive marking. In this case, the sclera may be a color on the respective Arcane or Radioactive slider, or an Off-Black color. 

The mouth is the main area affected by Flesh colors, but white markings such as Piebald, or Chalk range base colors- as well as the free marking Blush- allow a flesh color gradient where the skin is thinnest.
Skin gradients may use the lightest flesh tone slider on the left, while the mouth may use the darker or chow blue gradients.  The mouth may contain multiple colors, and may have gradients or scattered darker spots. If the dergon has an Arcane or Radioactive marking, the tongue may be brightly colored, picked from the marking's respective slider. 

Claws and Horns (referred to as Keratin) have many options. Firstly, they may use the Natural color range, any marking or base color used on the dergon, a shade of the chosen base color, and the White, Black, Off-White, and Off-Black sliders.
Keratin may also show markings. Gradients of up to two colors are allowed, as are stripes or spots of an additional color, and markings may extend onto the keratin- either with the marking's chosen color or with a darkening or lightening effect on the keratin's chosen color.
Keratin may show different colors on different parts of the body. For instance, the foot claws may be affected by an Arcane glow, while the wing claws may be a Natural color, and horns  a light pink while touching Piebald.