A simple RGB Color Picker.
Nothing fancy. In fact, I had Gemini 2.5 write the first draft of an "HTML and JavaScript only" color picker.
I modified it to have a shade of teal for the initial color.
This is an interactive note - you can use the three sliders to select a custom color.
There are improvements which could be made (yes it might shimmy) but this note is mostly a test of embedding static HTML+JS via an iframe.
Using Gavina, the Gemini drafted color picker is in:
/input/static/apps/rgb_picker
The corresponding index.md for this note then contains:
<iframe src="/apps/rgb_picker/rgb_picker.html" width="350" height="500" frameborder="0"></iframe>
Easy-peasy.