track color

Short answer: not possible.

Longer answer: Blue is the default color of a track. A segment – or the whole track when it contains only one segment – becomes red when it is selected (when tapped on the blue line in the map).

Why do you want to able to change the color of a track?

Makes sense. You could create a feature request for this functionality.

You can show multiple tracks in the map by assigning all the 5 tracks to one group. You can do this by opening the detail screen of a track and tap the Groups entry (you will find this under the section Overview). Create a Group and select this for the track. Select the same group for the remaining tracks.

Now go to the Favorites » My Groups and select the group. Tap the View button from the details screen. Now all the tracks are displayed.

To show the tracks in a different map than PE you could try the web app http://www.mygpsfiles.com/app/ on a computer and open the GPX tracks. With MyGPSFiles you can change the color of each track (and do a lot more).