If the pattern is one that you really want to make then buy all the fabric to make the quilt! As mentioned before you can always add to your stash for the red/white quilt gradually. Or maybe you can get enought to make the quilt and also stash. I personally buy all fabric to make a certain pattern. I have lots of stash that never seems to match a pattern that I want to make. Also beware that fabric colors can change from year to year. I have some lovelyt peach fabric I bought several years ago and have had a hard time trying to get more fabric to go with it.