My Pomeranian is peeing very dark brown/reddish color urine. She is acting fine and eating, playing ,etc. Can I wait until the morning for regular vet or is it an emergency?

This doesn’t sound like an emergency since your pet is acting fine, eating, and playing, but the very dark brown/reddish color urine is probably a sign of blood in the urine which may or may not be a serious problem. I suggest contacting your regular veterinarian first thing in the morning to schedule an appointment for an examination.