There have been several discussions on this site about patterns and copyrights. Just do a search to read them all. I believe that the copyright comes down to publishing the 'wording of the instructions to make a block' and not the block itself. Please read the other threads on the board. But honestly, unless you are going to write up the exact same directions as another published pattern and use the exact same fabrics, I do not think that you could contravene any copyright laws--especially just for a different colour take on a traditional pattern.