The Rainbow Denise Sets are dyed exclusively by Amy and sold only at KnittingHelp.com. Denise will still honor the warranty on these kits and will provide replacement parts if you encounter a problem. However the needles provided by Denise will not be colored.
If you needed a replacement set of needles for a rainbow kit, the current cost would be $5.00 per size, plus shipping which would be around $2 with the US. We only sell replacements needles in sets of two, as the colors vary slightly from batch to batch. A set of two needle ensures that they are both from the same dye batch and will therefore match.
As for the marbling. Our dye process is added after the needles have been manufactured by Denise. Therefore, any natural grain or irregularity in the original un-dyed needle from manufacturing will show a bit after it's been dyed. Denise has improved their manufacturing processes and the needles we receive are much more uniform and in most cases there is no grain. I'm looking at a set now under bright light and it's difficult to see any marbling or grain. All of the bright colors (pink, red, orange and yellow) look perfectly uniform. If I really look hard and squint my eyes just right, I can make out some slightly darker areas on the green. It doesn't in anyway detract as it's practically imperceptible.
We have sold hundreds of these rainbow sets over the past 8 years and they have been extremely well received. We get wonderful feedback from knitters who use them and adore them. We offer them with the full support of the Denise needle company.
I hope this information is useful. If you have any further questions, please let me know. I'll check back in on this thread.