Green in the sun, red in the cup RMI-25

[Shaman]

Pardon my ignorance of red coolant, but I have a question. I recently installed a coolant temperature sensor into my car, and went out this morning to check the level. In the sun, the coolant is puke green. In a white paper cup, it is red. I put half a bottle of RMI-25 in a long time ago, and wanted to know if this is the color it turns red coolant or if I need to get the coolant flushed? Any help is appreciated