Color coding messages in the BlackBerry Hub isn't totally new with OS 10.2.1, but it may well be one of those features that as a BlackBerry 10 user you weren't aware of. What's nice about this feature is that it isn't just your email accounts (if you have more than one) that you can have colors assigned. All your native apps such as BBM and SMS are included as well, but so are any others that have Hub integration - so the likes of Facebook and Twitter can get a touch of color in your Hub.
Being able to color code your messages in BlackBerry 10 isn't just about making things pretty. It makes it easier to visually triage your messages. If you know that you've set your Twitter mentions to blue and orange to yellow and BBM to purple it's easy to swipe through and get an idea of what you've missed. Each Hub notification gets a colored line on the left hand side to correspond with the color you've selected for that type of notification.
When it comes to setting things up you have a choice of using green, blue, orange, pink or purple. By default none of the notifications have colors selected, so to get things up and running you'll need to do it manually.
As you can see, it's super easy to do and while it doesn't really add a huge amount of function, you can at a quick glance view the accounts that are most important to you. I for example have several email accounts on my BlackBerry, but it's only the Mobile Nations one that I have colored - so if I dive into the Hub I can easily see which emails I need to read first. It's all about personal choices - something that BlackBerry 10 has become rather good at.