The colored background makes it hard to create a Spin editor...
But, I finally came across some colorizer example code that I was able to understand and twist into shape:
It now bolds all Spin1 keywords and sets background colors the right way (I think).
It also recognizes comments.
Update: Fixed keywords for VAR, CON, OBJ sections. Zip updated 7SEP18
Code posted 7Sep18.
Anyway, this is looking like it might work...
A 7-zipped Windows executable is below...
latest Exe (in .7z format) posted 29Sep18.
It requires the Parallax font be installed, but you probably already have it if you use the Propeller Tool.
For P1, it requires propellent to be in same folder as spinedit.exe
for P2, you need p2asm.exe and loadp2.exe (attached in zip file) to be in same folder as .spin2 file