Here are a few hints I use to pick up fabrics
1; On the edge of some prints, you find little dots of the different hues they used to dye, I usually choose the colour they used the least as a contrasting fabric.
2; Browse into a cross-stitch book,study the gradation they use to embroider a flower or a leaf. If you have the skeins of floss, bring them with you at the store
3; Your paint store sells the collection of paint chips or pick them for free at the display rack. If you pick the third colour from the top, the third colour on another card should match.
4. If you pick from your stash display your choices someplace you can see them often. If one does not agree, replace it. Let them sit for a couple of days,to make the right choice.
Sorry, my English is awful today, I can't find the right words or grammar or both.