Note that Graphite does _not_ work with a stylus --- in the web version the input is too jerky/disjointed, for the desktop, it won't react to a stylus in any fashion at all (for the Windows version).
SolveSpace does have some ability to control the color and fill of areas. It's nowhere near as powerful as Inkscape, but enough to make simple diagrams. The exported SVGs can also be edited in Inkscape.
https://paragraphic.design/