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Set an A value (opacity) and RGB color for the collision group. Color can be used to visually differentiate collision groups in the viewport in part programming sessions. For example, you might use red for a Robot-to-Cell collision group and a different color for a Robot-to-Robot collision group.
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This option only affects collision colors for objects in the viewport, collision indicators ( 
) are always shown in red.
Pairs
The two boxes opposite eachother in the Pairs section control which elements are evaluated for collisions in a given group.
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