To help quickly recognize my house keys that all looked alike, I made these simple but effective keys caps.

I wanted to use different colors of filaments for lighted environments but also to be able to distinguish them by touch for dark environments or use by the visually impaired.
So I made these different forms: circle, hexagon (6 sides), heptagon (7 sides) and octogon (8 sides).

Most of my keys were fine for the 23.5mm diameter size, but I had a slightly larger key that required me to use a 24mm diameter, so I uploaded those versions as well.

DAGOMA

Disco Ultimate

No

No

0.1

17%

For best result, ensure you use the finest resolution available.
Printing itself won't take too long as these are really small pieces.

Print two halves for a key.

You can then assemble them using cyanoacrylat glue (i.e super glue) or by soldering them.
I used this solution for my case as I got a Modifi3d finishing tool.