Lilac is just dilute chocolate. If you take away the dilute you get chocolate. A non dilute color like black or chocolate will only produce at best 50% dilutes and possibly none. That's why you end up with blacks or chocolates from blue and lilac crosses. The same happens with chocolate and black. Chocolate is recessive to black so if you breed a chocolate to a black you get at best 50% chocolate and possibly all black. Same thing with blue and lilac since blue is dilute black and lilac is dilute chocolate replace the black in the previous sentence with blue and the chocolate with lilac.
Are letters easier for you? B-black, b-chocolate, D-normal color, d-dilute. All genes come in pairs.
BB is black, Bb is black in appearance carrying chocolate, bb is chocolate
DD is normal color,Dd is normal colored carrying dilute, dd is diluted
therefore
BBDD is plain black that cannot throw blue or chocolate
BbDD is black that can throw chocolate
BBDd is black that can throw blue
BbDd is black that can throw chocolate, blue, and lilac
BBdd is blue that cannot throw chocolate
Bbdd is blue that can throw chocolate or lilac
bbDD is chocolate that cannot throw lilac
bbDd is chocolate that can throw lilac
bbdd is lilac
Now the mother contributes 1 of her genes from each pair so 1 B or b and 1 D or d depending what she has and the father contributes one so if we combine a few colors:
bbdd-lilac with bbDd-chocolate carrying dilute (lilac) each parent can only give a b so all offspring are bb-chocolate based, one parent can only give d so one of the dilute gene pairs will be d-diluted and the other parent can give a D-not diluted or a d-diluted. There's a 50% chance of either making our offspring have a 50% chance of bbdd-lilac and a 50% chance of bbDd-chocolate carrying dilute(lilac)
If our chocolate rabbit does not carry dilute and we have bbdd x bbDD Then each parent can only give b again making all our offspring bb and none of them black/blue and one parent can only give d while the other can only give D making all offspring have both Dd so all our offspring have to be bbDd-chocolate carrying dilute and you will not see any lilacs.
When we throw black in the mix we are just dealing with B instead of only bb. Any rabbit that gets a B is black based which dilutes to blue if they are dd. 2 chocolate based rabbits, bb, cannot make a black based rabbit because there is no B, but a black based rabbit since it can be carrying Bb and appear black but contribute a b can make a chocolate based rabbit. A dilute rabbit has to be dd and has no D to give so if you mix 2 dilutes you can only get dd or diluted rabbits where a non diluted rabbit can be DD and make no dilutes or Dd and contribute a d 50% of the time to make half dilutes and half normal colored.
Combining 2 heterozygous pairs (gene pairs that are not the same) like Bb with Bb (bb and BB would be homozygous pairs) will give you 25% only the dominant color, in this case BB or black with no chocolate, 50% heterozygous-Bb which appears the dominant color, black, but carries the recessive color, chocolate, and 25% of the recessive color- bb or chocolate. This applies to all combinations of dominant and recessive genes that only have 2 possible colors. Dd with Dd equal 25% DD, 50% Dd, and 25% dd. It is possible to have a gene set with 3 or 4 possible genes instead of just a dominant in capital letters and recessive in lower case letters.
Of course real life breeding does not come out perfectly 50/50. Each litter may have more or less of the possible colors than the percentages on paper because these are only the odds each kit could be a given color. Just like you may get some litters with mostly bucks and some litters with mostly does even though genetically they have a 50% chance of being either. If you breed lots of rabbits eventually the ratios do even out to the projected percentages.
