If this isn't the right place to post this feel free to move it.
I recently got an order in from shapeways of a custom keycap I made in the shape of a 3x3. I had to print in detail though and I wasn't sure if dying frosted detail (not ultra) is safe for the part. I tried using a sharpie but it doesn't work. It just comes out translucent dark purple.
Does anyone have experience with this or have any theories? I'm grateful for any help.

Frosted detail is made out of a acrylic polymer that has been cured with a UV lamp.

Acrylic can't be boiled or heated too much or it badly deforms. Acetone and other strong solvents also totally destroy it. Last time I used acetone on acrylic it caused it to deform and flake apart into a mush of soft acrylic chunks.

You need to use a disperse dye.

A lot of instruction online involve boiling or using very hot water. I'm not sure if these instructions are fabric specific but if you boil a frosted detail printed part you'll destroy it.

Looks like Jacquard iDye Poly is the easiest one to find. It'll probably take some experimentation to find a process that works.

EDIT: see here for more details: http://textilelearner.blogspot.com/2012/01/dyeing-of-polyester-fabric-with.html

Oh wow, I'm glad I asked before going ahead with it. I will probably just end up painting it then.
Thanks for all the helpful info!