Yea, grew up on B/W Kidpix. In this JS clone, some of the effects are also less pixelated, especially the fractals / mandalas. "Broken Glass" and "Wrap Around" gives me errors as well. It's not 100% perfect clone but it's amazing and the code is beautiful, performant, concise vanilla JS.
You can add the CSS rule "filter: grayscale(100)" to the body if it helps. I have no idea how black and white monitors worked though, I would guess they'd have less than 8 bits of brightness info?
It allows to see. I just tested on chrome dev tools. What it does not to is set the filling as it worked on the original app. Anyways, really nice memories. I was a child (6 yo) when I first touched those. Thanks for the hint to play with CSS. :-)