I also keep track of different colors I have in my own PC (personal collection) spreadsheet - for quick reference when browsing ebay or COMC for something I might not have yet.
As for TCDb, there is the "Detailed Add" - or if it is already on your list - "Edit Details" drop-down menu item. There, you can make multiple entries by putting your own notes on color, texture, patchwork, etc. I'm not sure how readily visible those Details are to other TCDb users. It doesn't seem to appear unless you click on the link to the actual card, then you can see your individual card's pink/green/blue collection info bar below the site-scanned images.