Creatures Caves

Colortrue breeds having those extra pigment genes and scattering pigments throughout the genome might mean you get an 'unsafe' genome for crossbreeding, with a fair chance for bad mutations if you breed them with breeds that aren't colortrue, but you get the same thing with CFE genomes as well... Also, having colortrue genetics has many positive effects too, and fixes some annoying problems with the normal, blocked-together pigment genes.

Here's the idea: Since the genes of two parents are lined up and spliced together when mated, with the offspring getting dna in chunks from one parent or the other between crossover points, the number of pigment genes and pigment scattering in the colortrue norns makes it very likely that the offspring of colortrues will have a good mixture of pigment genes from each parent.

Because each group of pigment values in a norn are averaged to get the final color (the groups being reds, greens, blues, rotations, and swaps), colortrue offspring have a very cool effect of being a color that is a nice mix somewhere between the colors of the 2 parents (i.e. A red colortrue + a blue colortrue will give you a violet/magenta/purple color, a green+blue gives you a turquoise/cyan/aquamarine color, a red+purple give you a magenta/mauve/mulberry color, etc...)

The extra pigment genes and pigment spreading in the colortrues also mean that whole pigment groups are a lot less likely to be entirely lost to random mutation or slight sliding effects from one parent having a few more genes; something that can cause drastic and usually undesirable effects in your color (for example, if you have a nice pink norn and you were to lose the whole red group, the result would just look washed out and too bright with no special color at all)

On the other hand, if all the pigment genes are blocked together, like in most normal C3/DS genomes, then you get the tendency for most or all of them to just be carried all together from one parent when breeding happens... This means that rather than a mix, you tend to get offspring that only favor one parent's coloration, with only a small minority or even no pigment genes from the other parent.

Even when there IS a crossover somewhere in the blocked pigment genes, the crossover will tend to mostly affect only one group, like the reds, greens, or blues, making the part copied over to the offspring just a tendency to a partial shade that looks nothing like EITHER parent's color, and even that bit still gets averaged out and muted by the other parent's pigment genes.

So, rather than ever getting any kind of actual mix of the 2 block-pigmented parents, you will instead see something looking just like one parent or the other; only occasionally with a randomish shift in the red, blue, or green part of their pigment. These occasional shifting effects of partial pigments are pretty much the same effects that have a decent chance to appear randomly with mutations anyway even if you have no crossovers or have 2 parents with the same exact colors.

This also means that if either block-pigmented parent has some pigment genes you really like, or a cool mutation in some part of their pigment or color bleed, you have a good chance (over 50%...) to either have ALL those pigment genes you want totally thrown out, or to lose whole major groups of them that are necessary to make them ever show up properly in future generations.