Tested holographic stickers recently

I definitely love the effect of these stickers (they are rainbow-y), but my order didn't look as good as it turned to be too dark, even grey, while the preview was pretty bright. I've ordered some regular stickers with the same design later, and they turned to be nice and light, so I'm wondering if the problem was about the type of stickers. If so – I d'love to be warned next time. But in general, I loved the idea and would probably order some more, but with other design.