You can inbreed. I don't recommend more than 1 or 2 crosses, and not to repeat it if you see deformities. I have done sibling to sibling and parent to offspring without problems. The further the relation the less chance of problems showing up.
Great thanks for the info. Do you know what to look for when breeding, like out of a pair who would have the dominant gene and what colours would be more likely to be prominent?