Farmville- Why do I have a colour changing ewe in my congo line?

I was breeding sheep a bit ago, and I noticed a ewe that kept changing colour in the congo line. The one was adopted, but everything I've read said the grandparents and such don't come into play. One was a two toned ram (blue and purple) and the other was a dark blue ewe. I didn't have any potions at the time and I'm still waiting for results... It says they'll be done in two hours. I'm not a very active player, and that's the only sheep I've adopted.