I've done the same as Gary - have a tote with various harnesses from these trucks. If replacing existing I used those to keep it looking stock.
For anything else (add-ons) I bought rolls of wires from acdcwireandsupply on ebay. Very happy with their stuff. Numerous colors: solid and striped.
I don't know that I'd lose much sleep over keeping them stock colors if you don't have easy access to a jy or parts truck you can strip. Once it's taped or put in a loom, you'll never see it
The important part is using different colors as much as possible. Avoid grabbing a roll of red for hot and using that for everything. Makes troubleshooting painful in the future.
Scott
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Camano' 1986 F250 Supercab XLT Lariat 460/C6
'Chanute' 1980 F350 C&C 400/NP 435 - Gin Pole
But there ain't nothin' wrong with the radio