For performance reasons, the zoomed-out preview is not generated from the full-resolution image, but rather from a scaled one. We have seen cases when comparing a full-resolution export with the preview, or with a scaled-down export without ‘high-quality processing’ turned on, contrast (and perceived colour) differs strongly.
If it looks yet again different on pixls, then there is probably a colour management problem.
Thread mods - if this shouldn’t be here - let me know and I’ll move it to Darktable.
I have tested my browser (Firefox on Linux) here and it seems to work as intended. So too if saved to local drive and viewed via Gwenview which is my default image viewer.
Try two exported versions. One with and without high quality reprocessing. Setting no usually gives a result that looks more like a scaled screen preview and setting yes will have things more like what it looks like at 100 percent… This has also been discussed at length a few times on the forum… As for those color edits I sometimes use the CLUT module. The green blue and skin patches can be used or custom matched to a color selected in the image and then tweaked using the color saturation and Luma sliders…