I bought an Attitudes by Renee top a while ago. They said it was plum. It's very nice, fits well, well made, not static, not sweaty, doesn't bobble but I am devilled it I know what colour it is. It's a sort of deep pink berry tone, blue toned. Maybe a dark magenta. Not sure it's plum though.
I bought another Renee top recently. I blame the stunning Sharon who modelled the thing. Grey animal print number. And it's lovely. Doesn't make me look like Sharin but that would take a miracle rather than a camisole top. Anyway it's blue not grey! In both cases the colours were a bit of a surprise.
I bought a yellow Tig bag. It's flipping mustard not yellow at all. But at least on the screen it looked mustard so I knew what I was buying.
In both cases it doesn't matter but it does make buying things difficult. Especially if you're trying to match in with your current wardrobe or decor.