Artifice is a special gene. You may choose one existing non white-spotting genes or a specific body part (claws, mane, horn(s)) on your colonist and choose a different colour range for it from that specie's base coat colour ranges or the free black/white ranges on the main Genetics page. For example, you might have a white tsabhua with slate sable.
Artifice follows the darker/lighter rules of the marking/body part and must originate from a colour slider from the species.
Two toned markings such as Underbelly may have artifice affect only one of the two, at the artist's discretion.
The colour of the affected marking/body part must come from one of that species's colour ranges on their information page. For instance, this is the tsabhua's page and list of colours. It can be adjusted slightly from the range for darkness, saturation, or lightness but should not change the hue at all and should at least appear to be from one of the ranges.
Artifice does not just allow you to ignore colour ranges completely.
Value (darker/lighter) rules should always follow the same rules as if artifice wasn't applied. For instance, above: The original slate tsabhua has artifice. The example on the left would be incorrect, unless the tsabhua also had flaxen, because the mane is lighter than the base coat.
Exception: In the case of dark markings on black colonists - those can be lighter than the base coat.
In an effort to maintain quality, if colours are chosen that are visually offensive (basically, if they look bad) we may request adjustments. In these cases, we will often give visual examples of better-matching hues to assist you