Security Battle Droids are versions of Battle Droids made by the Seperatist for security measures. They have red painting on their torsos to define their rank. Security Battle Droids appear in three sets changing each time. They only appear in Episode 1 and 3.
The original Security Battle Droid had a red tip on its torso and head, while the other parts of it remained normal.
When the 2007 Trade Federation was released, Security Battle Droids reappeared after a 6 year absence with an entirely red torso instead of the small red tips.
They appeared again in the 2011 version of the Naboo Starfighter with printing in the middle of its torso with tan coloring that matches the tone of the droid itself. This set includes two of them.