After buying the Nödmast lamp from IKEA I liked everything about it except for the colour it was producing, so I made a replacement cover/diffuser for the LED.

First take the original one out, you'll just need a flat screwdriver to pry it out of its socket (relatively low force). Then align the notches on the printed cover/diffuser and push it down until it clicks in place. And you're done!

I have a lot of red ambient lighting at my place so I went for the same colour, but I imagine yellow/orange/green/etc can also look interesting. Before anyone asks, I've printed it in PLA and haven't noticed any temperature-related issues so far.
I used 0.4mm nozzle with 0.08mm layer height, but I think it'll work with most settings with supports added.
Included the .f3d design file in case anyone wants to edit the model.