Hi! I made special lightbox for people who don´t have multicolour printer!!!
You print both parts, by a hole on the side insert the led lights and then just glue the two parts together.
It is designed so it can be printed multicolour even if you dont have multicolour printer. You just have to set up automatic change of colours in your slicer and then print colours one by one. 
Recommended size is 200mm and recommended height is 2mm 
I hope you like it :)