Add 'random value' as an option for the set colour parameter in the Project Logical Editor

After asking around it seems it isn’t possible to apply random colours to existing tracks. Would be nice to be able to do this for those folks who like a bit of colour diversity in their projects. Adding a ‘set to random value’ option as an alternative to ‘set to a fixed value’ for the ‘set colour’ parameter in the PLE seems like it might be a fairly simple thing to implement and way to achieve this.