Alleles linked to Pattern

[Nomad]

I think I read somewhere that recessive opal (I think?) was linked to pattern and quite difficult to cross to another pattern. Is there other genes linked to pattern or color which can make them harder to replicate in another / color and or pattern?

Thanks
Nomad

[AdamArcher]

I have a terrible cold at the moment so my brain might not be firing completely, but spread is also linked to pattern. I can't think of any others at the moment, if I do I'll come back and edit this comment.