Have you tried calling this company: https://www.andfel.com/custom-printed.html
I've used them in the past for custom orders with good success, they may be able to help.
Here is another company I've used for custom nylon ties: http://lecoplastics.com/cable-ties.aspx
I have ordered custom sizes for special applications; their site says they can custom color for a fee.
You can dye nylon by boiling in fabric dye- I used to do that for coloring RC car parts. Probably kind of a dull red, though. Wouldn't cost you much to experiment and report back.