Blending modes should now be identical between firefox and chrome browsers, I was able to personally confirm that they are equal - though there may be some things that I forgot to test still.

I've also added a new tool - a colour replacer. Clicking on something you've drawn will change all pixels of that colour to whatever colour you have selected, within the same layer.

I have allowed the custom colour picker to pick from the canvas, but firefox does not support colour pickers outside of the canvas area, that is a browser-level issue and not one I am able to personally fix. The only solution is to use a chromium-based browser (google chrome, brave, etc) if you'd like to use the chromium-based features of the canvas. Chrome, Opera, and Microsoft Edge all support the colour picker. Firefox does not.

An alternative I can think of is a downloadable desktop version of pawprinting's drawing system using electron that would contain the chromium-based elements and not require a browser installation, though I have a feeling people would be uncomfortable installing something like that.

I would also like to repeat here that I'd appreciate a bit of leeway when things go wrong - I am a single individual working on this site, for free, at a substantial personal cost. I have no monetary incentive to keep this site running or working, I do because I enjoy seeing what people create and generally people really enjoy what I do.