Solid Colours

On the Home tab, in the View group: Select Solid Colours to apply a colour set to the Source and/or Destination solids currently displayed in the Animation window.

Note that you can set also colours for solids from the Animation tab of the Scenario Settings window. When you save an Animation View, Colour Set settings are also saved as part of the Animation Layout. See: Reset View

Solid Colour Sets

Define (and Apply) a Colour Set to Solids

Click on the ellipsis [...] to define a Colour Set and apply it to the Source/Destination solids in the Animation window.

Right-click on the Solid Colours node and select an Add option: