The Battle Droids are the Trade Federation's main foot soldiers fighting against the Galactic Republic. Battle Droids can be made quickly and in large numbers without any training required. However, they are rather weak and clumsy in battle often falling down or getting destroyed by the superior Clone Troopers of the Republic.
The regular standard battle droids are the most common and disposable of all the droids, often carrying a regular blaster rifle. When destroyed or damaged, they are often scavenged and rebuilt.
The Geonosian battle droid is a dusty red battle droid, but besides the colour its pretty much the same droid, the colour probably helps it in its geonosian landscape and terrain.
The commander droids are the highest ranking battle droids often in command. They are also more tactical than other droids. They often have blue or red coloring to identify them from regular battle droids.