Does the partner mechanic allow you to have two commanders of different colors in Commander?

Under normal Commander rules (CR 903.3), you designate a single legendary creature as your commander. However, the Partner keyword (CR 702.124) creates an exception: if both chosen commanders have Partner, you may begin the game with both in the command zone simultaneously.

Your deck's color identity (CR 903.4) becomes the union of both commanders' color identities. So if one commander is White/Blue and the other is Black/Green, your color identity is White/Blue/Black/Green, and your deck may include cards of any of those four colors.

There are a few variants of the mechanic to be aware of: standard Partner (pairs with any other Partner creature), Partner with [Name] (pairs only with the specifically named creature), and Friends forever (pairs with any other Friends forever creature, introduced in a crossover set). All three variants allow two commanders.

Both commanders follow all normal commander rules independently: each has its own commander damage count, each costs 2 more generic mana for each time that specific commander has been cast from the command zone, and either can go to the command zone when it would move to a graveyard or exile.

Example: You choose Tymna the Weaver (White/Black) and Thrasios, Triton Hero (Green/Blue) as your two commanders. Your color identity is White/Black/Green/Blue, and you can build a four-color deck. Each starts the game in the command zone, and you may cast either one on your turn.