How do you make different-colored blocks?

[A quite MEDICal Derpfish]

How does one make the blocks in a level different colors, like in Doormat(?)'s level where  visits our forum, he uses that with the avatars.

[Fussmatte]

Push F10, then hold Ctrl and use the arrow keys to select a tile.
Only works in 2.1 and above.
[Note added 2020 Feb 8: the upcoming VVVVVV: Community Edition will have a different keybind than Ctrl. Currently it is Shift+Ctrl but it is subject to change.]

[FIQ]

Direct Mode let's you do that. If you cannot get 2.1, tough luck. If you can, go and get it. In the level editor, press F10 to enable direct mode in a room. This will make you edit the room without the "autocorrections" for wall layouts, spike direction and such, and instead lets you chose exactly what tiles to add. To chose a tile, hold CTRL. This will get you the list of the tiles. All tiles are the same no matter what tile color you chose -- this will only affect enemies, conveyor belts, warp and platforms. The same applies for tileset, which only control which background to use. However, if you use Space Station Tileset, you get a different selection of tiles.

[Fussmatte]

DITCH MY POST, LISTEN TO WHAT FIQ SAID.