Infinity dress -are the colours pretty true to what is on the website?

I had to look these up as never heard of them! They look quite clever LOL

I would ask them if they supply swatches of the fabric so you can see the colour. I was able to do that with JJ's House so I could choose the right colour for my BMs dresses.

I agree with yorkshirelass. I also ordered a swatch of fabric from but from babroni to make sure the colour was true to the picture

I wore a blue one of these as a bridesmaid once, and honestly it was the most vivid colour (although that's what the bride chose, so I guess it was true to colour).
I would mention though, it was a very uncomfortable dress to wear. Both I and the other bridesmaid were uncomfortable having our arms on show, and the infinity dresses only have one way to style with sleeves that doesn't fall apart as soon as you move. I'd make sure to think about exactly which of the possibilities are actually practical before you invest

The photos on the site will not be so much the problem as the device settings that you are using. Most people have their screens set way too bright and far to saturated colours and so sage green or mauve are really going to struggle to be seen properly.

Even part of some phone advertising they say things like "increased contrast and vivid colours"

The safest way is to have a swatch or buy one on sale or return.