2 tips worked for me when i started quiliting
#1 use the colored dots on the selvage of the fabric to match colors... you can use fabric frm a bunch of different manfacturers that way
#2 when trying to get the value (light, med, dark) cut a small piece (i usually just clip an inch of the corner) put all the ones you want to use on the copier & take a black & white copy.... taking the color out of it leaves just the value...