Please help me!

I just noticed my line/tubing was very discolored. It is a dark purpley/blueish color, only about 3/4 of the line was discolored from about 1cm from my site. The insulin inside the cartridge and start of the tube was clear so im assuming its the outside of the tube that changed color. I was wearing white and gray clothing so it mustn’t of been dye rubbing off my clothes. I decided to change the site,tubing and insulin just to be safe, but does anyone have any ideas of what this could be? Tried to give as much info as possible. Any help is much appreciated!

Did you ever find the reason for this? The exact same thing happened to me yesterday after 10 years of pumping and no obvious dye from clothing possible.