Summary

This is a multicolor remix of Byctrldesign's design (found here: http://www.thingiverse.com/thing:525066). I printed it using ReplicatorG and a Flashforge Creator Pro. It's in red and black ABS. 5% infill.Both colors extruded at 235°C with the heated bed at 80°C.

Instructions

In ReplicatorG, Select Gcode from the menu, then Select Merge .stl for DualExtrusion.

Browse to the stls for the left and right extruder. I used the left extruder as the outer color and the right extruder as the inner color.

Select a path for the gcode and click Merge.

You'll get two slicing options boxes, configure them as you normally would. I used 5% infill and 235°C extrude temps. (Use whatever extruder temp works best for your printer and color)

Once it's done, I manually edit the gcode to drop the headed bed temp. (If I run it at the default 110C, my prints curl up)
Change the S110 to S80 (or whatever works best for your printer)

M109 S80 T0 (set HBP temperature)

Print it and enjoy a multicolored phone holder.

Multi-color phone holder / stand