This is a keychain I made for my Duke, designed in Inventor Professional. I made it for manual colour change, at 2 and 2,5 mm. The colour combination is your choice.
Personally, I scaled it in X and Y axis (because it was a little big for a keychain) and leave the height in 3mm so I could change colours (I used 0,25mm layer height).

I´m from Argentina and my english is a litlle rusted... But if you have any question just ask it!