Do I need to wash the fabric I just bought for quilt making?

It's my first time making a quilt and I'm learning as I go along. I created a design and bought fabric (100% cotton). So now I'm ready to start cutting the pieces but it occurred to me that I have light and dark colors. Is it possible that the colors could bleed into each other when the quilt is washed? Should you always pre-wash the fabric before you start cutting to keep the colors from bleeding later or am I just being too cautious?