I have been reading all the Copic forums for years and, being completely obsessive and having a math/spreadsheet background, I put together "fill-in-the-blank" charts that show Copic marker matches for all of the Stampin' Up cardstock (including all in-colors and all retired colors) and for all of the Papertrey Ink cardstock.
Just download and/or print it and fill in the blanks with the Copic colors that you own.
You can find the Copic post
here on my blog. The post gives all kinds of tips and hints on Copics. Then the download is in the left column.
Hope it helps!