Nice to see progress on the browser, but it doesn't seem yet to have proper colour management. I use a wide gamut screen and untagged shots are being over-saturated. There should be a way of forcing untagged shots to replicate sRGB etc. Firefox implements this really well and there's a great test page here. Lots of nice stuff though!
May be Chromium base 58 will get better profile support
But in Chromium bug tracker there are mana open requests/bugs about WideGamut and forcing untagged content to use sRGB.
It is the chromium code base failing with ICC.
But the Vivaldi team cant fix this.
If you need support of forcing untagged images to sRGB please create such issue at https://bugs.chromium.org/p/chromium/issues/list
Looking at the test page Words posted - if I understand correctly the Vivaldi (current snapshot 1.8.770.46) is already doing things correctly... the left image does not change when I mouse-over it, the right image gets more contrast.