Bloxels
thingiverse
Print out cubes of different colors and set up the base grid in black. Download the app to get started. Check out this video for an overview: https://vimeo.com/130132880. The app is available on both iOS and Android platforms. I'm not affiliated with the company, but I tested their app to see how well it worked. Their standard grid measures 26x26x1.27cm, while mine is a custom size of 8.3x8.3x0.4cm - perfect for printing on a wider range printer. Despite some minor issues with filament color variations and lighting configurations, the app still performs quite well.
With this file you will be able to print Bloxels with your 3D printer. Click on the button and save the file on your computer to work, edit or customize your design. You can also find more 3D designs for printers on Bloxels.