Actually, I was considering it. But I've decided not to, because most of my profit is made from the sale of the new needles, not from the coloring improvement, so I'd have to charge more than would be reasonable for just coloring. It's a better deal for both of us if you do the following:
I recommend ordering a new set from me, and selling your other needles. You can do the color upgrade for a $20 cost to you.
Here's the cost outline:
Order from me for $64.95, that includes US or Canada shipping.
Sell your other needles, you can get $45 plus shipping for them on eBay, here's how: Sell the brand new needle case and cables I send you, with the Denise literature, just swap in your un-colored needles. Denise needle tips only improve with wear (unless you let your dog chew on them or something), so I think you can with good conscience sell that described as a brand new set, just clean those needle tips well.
It used to be that Denise needles sold as low as $39 on eBay, but no more. The Denise needle company is no longer selling wholesale needles to eBay stores who sell the kits below retail value, so you'll see that all the sets on eBay are selling for $49.95, unless it's a rare individual selling their single set. So you can be very competitive by listing your set for $45.
So then the colored needles have cost you $20, and that's better than I can do as a coloring service! Plus, you'll have supported KH, because I'll have made twice the profit than if I just colored the needles for you at that cost to you.