I made the LED Brain per djholt's instructions with a few minor changes. I printed the brain without any modifications to the STL files as djholt provided. Here is a list of materials I used for printing and the LED's I used to get to get the color changing effect. My daughter is going into the medical profession so I made this as a gift for her since she likes this sort of thing.
I printed all components using a Lulzbot mini. I had to reduce the size to .97 in Cura to get it to fit.
For the LED's, I used 5 mm RGB slow rotating LED's. I have three LED's wired to the AAA cell battery pack. I did not use resistors. The LED's will stay on for about 4 days continuously without a battery change.