Norm Murray authored May 11, 2015 and Øyvind "pippin" Kolås committed May 11, 2015

From the GIMP UI it's very tough to tell what the values represent, so changing 'Amount of [color]' to '[color] Channel Multiplier]' will help understanding of what the UI is representing.

To go with this, set default value to .333 so a default conversion is approximately luminosity neutral.

Lastly, pull the value range toward a reasonable range -10 to 10 is extreme