Practice on a large dry erase board, holding your elbow up and moving your arm just as you do when quilting. Try a pattern that doesn't require precision, like flowers, leaves, hearts, loops, etc. Don't try a pattern that requires precision, like something geometric that repeats and all the repeats are identical. It's better to do what you are good at after practicing, instead of doing an inferior execution of a more difficult pattern that you haven't become adept at yet. Since you have all those colors and seams to follow, it would be easy to quilt something without marking the top at all, following the colors. That would also emphacise the layout, which would look nice.