This doesn't work well with browser extensions which darken web pages color themes (like "Dark Reader"), as all the painting colors will be rendered to black.
I know It might be obvious but having those extension always on I tend to forget they sometime can cause some visibility issues, so I'm leaving this here :)
There's a global setting in Dark Reader to "Detect dark theme" pages -- when that is enabled, this game is automatically detected as using a dark theme so the Dark Reader plugin is disabled for the page.
But the Clone-a-Lisa page does not use a native dark theme, and the problem seem to be just with the paint colors, which in my case for some reason are altered by Dark Reader. It could also be that it was a temporarily glitch as I've noticed that color manipulation by Dark Reader can be inconsistent at times (could be due to DOM loading timing and stuff like that).
I know It might be obvious but having those extension always on I tend to forget they sometime can cause some visibility issues, so I'm leaving this here :)