- Old PC game - 90's or possibly early 00's
- Single player
- Campaign levels were based around capturing the enemy base in a team on team match
- Multiple ground Vehicles similar to Battlefield 2/3 such as a fast Buggy used to run people over and slightly larger slower vehicles with guns etc
- Multiple weapons that you could find in the level like any Deathmatch sort of game
- One team was red and one team was blue
- You could switch between the red and blue team during the campaign which would make certain levels easier because you would start at the other base.
- The setting was just some humans with some guns.
Only thing that comes to my mind due to mentioning blue/red teams + vehicles (and released in 2001) is 'Halo: Combat Evolved'. But think that teamplay was multiplayer so probably not the game you're looking for.