The coloured foreheads are like eye colours. Biologically they don't serve a purpose but the people make them important. There is indeed space travel between planets during my "main" timeline. I have the low tech pre space age timelines for many planets dealing with them before space travel was a thing when they were still primitive and the space age timeline where the different worlds interact and stuff. The technology level of this main timeline is quite a bit higher than ours in weapons, gadgetry and pretty much everything else (except for the lack of stuff like nukes) mostly due to the highly useful energy crystals powering basically everything.
The coloured foreheads are like eye colours. Biologically they don't serve a purpose but the people make them important. There is indeed space travel between planets during my "main" timeline. I have the low tech pre space age timelines for many planets dealing with them before space travel was a thing when they were still primitive and the space age timeline where the different worlds interact and stuff. The technology level of this main timeline is quite a bit higher than ours in weapons, gadgetry and pretty much everything else (except for the lack of stuff like nukes) mostly due to the highly useful energy crystals powering basically everything.