Alright, maybe a bit more than 20 mins. It's ugly, it's rudimentary, but it works. Feel free to fork it. The color/palette generation functions can use some work and I am not a designer.
Obviously it was a bit of a facetious comment, and props to the author for building a full iOS app. This is definitely not that.
*I have a bunch of color related function code snippets I use for dataviz, so I did not write the utils file "from scratch" just now. Also chakra-ui is a great component library that helps with quick prototyping.
I'd be really interested in seeing someone do that in 20 minutes. If you ever decide to do that, please post here.