New Post: shape random colors

It might just be impossible...

I was wondering if I can give every shape a different (random) color without creating 100 categories first. Tried something like this:
Dim red as Integer
Dim green as Integer
Dim blue as Integer

red = 255
green = 0
blue = 0

Then in a loop working on a shapefile called sf everytime a new shape is being created:
'change colors by sort of random
red = (red + 50) Mod 255
green = (green + 78) Mod 255
blue = (blue + 134) Mod 255
sf.DefaultDrawingOptions.LineColor = RGB(red, green, blue)

Somebody could predict I guess, but all shapes now will get the last created color. But on a single shape I cannot fiend any properties for the color.

Anybody ideas if something like this is possible without creating a new category for every single shape?

Thanks in advance!