The Red Trail is a sweet little slice of singletrack. It connects the Colorado Trail near the West Ridge to the West Aqueduct Trail, the Horseshoe Gulch Trail, and the other excellent trails located in the Soda Park area near Breckenridge/Frisco/Keystone. This area abounds in loop trail options and the Red Trail is a nice option to include in the mix.
The trail is a great steady climb up to, or off of the Colorado Trail. Other than one very steep switchback about a half mile from the intersection with the Colorado Trail, any intermediate skilled rider can can handle the minor obstacles found on this trail (one tiny section is washed out and should be walked). Views of the Ten Mile Range are awesome and, when in season, wildflowers are abundant. Pass through dense forest and wide open meadows. There's even a nice stream to follow for a bit.
The trail follows the Soda Creek drainage. This trail has quite a bit of northern exposure and is generally one of the last trails to melt out after winter.