Colour-coding your tracks can be an extremely useful tool when it comes to mixing. It enables you to quickly acknowledge what you're listening to and jump to it without hesitation.
This can be particularly helpful when you're attempting to glue together 15 or more tracks. Now, you're probably thinking that colouring tracks isn't very ground-breaking when it comes to mixing techniques? Possibly. But Logic has deeper functionality that enables you to take track colouring further.
Take three separate groups of tracks. For this example, I'm going to use Drums, Guitars and Vocals.
Open up the Colour Palette <OPTION C>
Colour the Drums BLUE
Colour the Vocals RED
Colour the Guitars GREEN
It starts to get interesting now...
Select just ONE region of the Vocals.
The one that is selected is partially black.
Now hit <SHIFT C>
As you will notice, all of the Vocal tracks are selected in one go. You've just used the 'Select Equal Colours' command.
This can be a very powerful tool. With groups of tracks selected at once, you can instantly take control over the arrange page and speed up your work flow.
Hit 'S' and everything in the group is soloed
Hit 'M' and (you guessed it) they're all muted.
All of this came simply from selecting one region after colouring. It works in piano roll too.
So, as you can see, colouring tracks isn't just to make your session look pretty – although it does that too – but it aids with your visual recognition of tracks and, more importantly, allows you to take more control.