I used three programs to make this: Stella 4d, Geometer’s Sketchpad, and MS-Paint. You can try Stella for free at http://www.software3d.com/Stella.php.
I’ve lost count of how many tessellations of octagons have appeared here. This might be the fifth one.
I saw a tessellation similar to this on Facebook, and used Geometer’s Sketchpad and MS-Paint to re-create it with colors of my own choosing.