Darth is right about kois being marbles(as expressed by you admittingra his color has changed slightly since getting him).
But breeding marble to marble doesn't make it skip a generation.
Breeding koi to koi you won't necessarily get koi. This is because the marble gene is, for the most part, unpredictable. getting a 'fancy' marble is up to luck in part with the genetics.
You'll get a mix of solids,multies,marbles,butterflies...it's a grab bag really.
If one is orange or yellow as opposed to red, I'd try to find a match for that(another orange for an orange or yellow for a yellow) otherwise your fry will show red(unless it carries the other color). But this is just me since I try to avoid red as a personal preference.
here are a couple articles you may find interesting for breeding marbles.:
some info #1
Some info #2
@Darth, I would like to see where you're getting this information as I've bred marbles myself. o.O