The alien skin tone appears to be a special case. While one will be shown as 'dominant' and one as 'recessive', the game itself does not treat any normal skin tone as dominant.
In SimPE, these genes will be shown as 'SkintoneRange'. For example, a baby who gets a gene for tan skin and one for dark skin may have tan, medium, or dark skin. Within that range, all skin tones are equally likely, and which one the baby has is determined at random. However, if a Sim receives two genes for normal Maxis skin tones, those genes define the ends of a range in which 1 is light skin, 2 is tan, 3 is medium, and 4 is dark. It should be noted that, while alien eyes are dominant, the alien eyes will look identical to brown ones, should the Sim not also express the alien skin tone. The other will be carried as a recessive and will be shown as such in SimPE. That color will be visible, and that gene will show as 'dominant' in SimPE. However, if the baby gets two dominant (or recessive) genes for eye color or hair color, one will be randomly selected as 'dominant'. If a baby gets a dominant and recessive gene for eye color or hair color, the dominant color will always be visible.
The game considers certain eye colors and hair colors as dominant and some as recessive.
