The green on the mounting section of the bracket has been seen on a ton of original examples I've seen. Depending on year and time it can be a single or double stripe
Have never seen (appears to be redo oxide color in your picture) on any of the ones I've seen - so IMHO would not consider it typical> since the color is so large you might be on to something with the idea that it was a spill rather than a mark. I do have examples of the idler with a mark that color on the arm portion.
As for the arm marks those related to application and time period but have never seen that large of a mark on the arm. This couldn't be someone with a rattle can early in the cars life could it. Have plenty of examples of an owner or kid with red, blue or orange just going crazy under some otherwise original or slightly modified cars.
Just grasping for answers