I removed the old fan switch and forgot which color wires go into the slots.

I assume black wire is L.

I have gray green purple wires

We won't have a clue unless you tell us the make and model. Where are you located and what color wires are in the ceiling box?

Here are some other color combinations:

L - Black, 1 - Grey, 2 - Brown, 3 - Purple
L - Orange, 1 - Black, 2 - Yellow, 3 - Purple
L - Black, 1 - Grey, 2 - Brown, 3 - Green
L - Grey, 1 - Yellow, 2 - Purple, 3 - Black
L - White, 1- Black, 2 - Blue, 3 - Yellow

Didn't find your colors.
Do you have another fan in the house like this?