You can change the color of an action within MonkerViewer by creating a file called settings.txt in the same folder as your MonkerViewer executable.
Each line in the file should read:
action = color
Where the action can be any keyword action such as call, fold, allin or a fixed betsize such as 75% or 12sb. The color is given by 3 integers between 0 and 255 describing the RGB value of the color.
Example line to set the color of a 75% betsize to red:
75% = 255,0,0