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That can happen for sure.
Have you seen old neon MTBs that are lighter on the top than they are underneath?
Lots of paints have poor UV protection and lose their colour. The helitape just altered how much light could hit the paint in that specific area so you get fading rather than colour being removed when the tape comes off.
The stuff from Chris at Cycle Wrap is supposed to be really good for UV and helps prevent this effect... I don't work for the guy btw... I'm just passing on what he tells us!
There are some lovely faded stripes across my/Dammit's old caad12 where he used 3m helitape for a framebag. Is paint not powder though.