I don't agree. Paisley is a well-known pattern type and some people really dislike it. "Shirt without paisley" is not a common request but its meaning is clear (if you do an image search for paisley you get lots of fabric images, so it's not like search engines don't know it.) I'd say the same for "shirt without red buttons." In general the pattern <article of clothing> without <feature> shouldn't be that difficult for search engines---especially since many are tuned for consumers.