Heya,
They need to be placed on a floor tile, not sure if they need to be on grid or not.
The red colour means they’re not attached to a tile properly, if you place one on a tile it will snap to it and turn blue.
Sometimes they stay red which usually means they need a different tile
or sometimes they will just become red at random, in which case you drag the launch pad a little bit off the pad and let go and it will snap back onto the tile and turn blue.