What is the red and white bar on the status screen?

Pretty sure the game explains our when it first appears, but the game can also throw multiple notifications at you and it's easy to miss.

The bar is your honour - you start neutral, and then as you do good or bad deeds it will move appropriately. Honour then affects how people react to you.

This is the Honor Bar. Here is a good webpage that explains it:

http://www.powerpyx.com/red-dead-redemption-2-how-to-increase-honor-level/

From the link:

In Red Dead Redemption 2 you can increase your honor level to unlock new clothing and get access to the missable honor mission...

To keep track of your honor press [d-pad down] and check the bar [at] the bottom of the screen. If the bar is on the left (red) it means dishonorable. To the right (white is honorable).

Benefits from increased Honor

You can see your honor benefits in the Pause Menu under Player, General, Honor.

• Rank 1: Better look from corpses.
• Rank 2: 10% off in all stores.
• Rank 3: New Outfits become available.
• Rank 4: Get access to optional chapter 6 honor mission ‘Do Not Seek Absolution’.
• Rank 5: 25% off in all stores.
• Rank 6: New Outfits become available.
• Rank 7: 50% off in all stores.
• Rank 8: Nothing, just peace of mind that you’re the most honorable gunslinger in the wild west.