You can actually remove the colorbar completely quite easy.

1. Run REGEDIT as administrator
2. Open HKLM\Software\Classes\Drive
3. Change the value for the key TileInfo. Remove the phrase "System.PercentFull;"
The key should read the following:
Before: prop:*System.PercentFull;System.Computer.DecoratedFreeSpace;System.Volume.FileSystem
After: prop:*System.Computer.DecoratedFreeSpace;System.Volume.FileSystem
4. Restart windows explorer (open task manager, and kill the process explorer.exe, choose File, Run and type in explorer.exe)
5. Now open Computer to see the absense of the colorbars

Note: This method does not disable the warning which occurs when free space falls below 10%. It does only remove the anoying red bars.

Zkouset se mi to nechce...