
The platform the player is supposed to get to is hard to get gel on, so flying to it's a more viable option. Sp_a3_portal_intro, the underground conversion gel test. Anything unpaintable should have an in-game justification. Take care to not diminish the realism in your map. However, displacements are typically reserved for more organically shaped surfaces such as cave walls.

When gel ends up in unplanned spots, puzzles can break. When designing a puzzle, be very mindful of possible exploits that may come of implementing gel as an element! It is generally very easy to exploit, and it should therefore be handled somewhat restrictively. Whatever the case, you can change it to pure white with this console command: portal_paint_color 255 255 255 255 (requires map restart). This gives rise to the thought that it was an intended change, possibly to make it blend in better with darker areas, or so it's more visible on white surfaces. How Valve could have missed this is not very clear, because at least one Art Therapy map used conversion gel, so they must have noticed.

There is some evidence and debate saying that the conversion gel was originally pure white, and that the current gray color was an accident by Valve, made while developing the Art Therapy maps. If your input device can be activated rapidly, consider having a logic_relay do the spawning inputs so that you can temporarily disallow the env_entity_maker from spawning more paint bombs after your device is activated. This alternative method will allow multiple paint bombs to be used at once, greatly increasing the chances of two bombs colliding with each other in midair, which can be a simple nuisance, or a clever trick to solve a puzzle. Alternatively, you can use a logic_timer instead using the output above, just change OnExploded to OnTimer. This how Valve does their droppers in Portal 2.

The game will recognize what it is though. Note: Hammer may warn you that this is invalid.
