I guess I visualize. I haven't ever done a quilt exactly by the instructions, and never in the colors shown (and most of the time I do not use a pattern for the whole quilt, but just take a block pattern and I make up the arrangement)
I am working on a quilt now that is entirely original - I drafted a new block and am making up the arrangement. I'm really excited about how it is turning out.
I have a lot more original ideas than will ever get made into quilts, however. And lots of times they don't turn out quite as good as I expect them to.