I had that problem when I first started sewing (pre-quilting years). With sewing, I would try to come up with an idea of what I really wanted to do ahead of time & at first I would trace the outline of the garment from the pattern's package so I could just focus on the shape of the garment, rather than the color or fabric texture.
Now, thanks to technology, I often will pull out my iPhone & look at it through the tonal filter on the camera app so I'm not influenced by color when shopping.