Old light wires 2 red 2 black 2 green new light fitting help??

If you are unsure you should really have a electrician come over and fit the light for you. from what you are saying it sounds like its the end of line for the lighting circuit, therefore you have one permanently live cable and one switch cable. if you join the two red wires together at the fitting in a suitable connector block or wago connector, put one of the black wires in the live pot (the switched live) on the fitting and one of the black wires in the neutral pot and the green/yellow wires both in the earth pot that will solve your problem but as i say really you should consult a electrician to test it and wire it up safely.

The two reds together in a connector. One of the blacks is a switch wire, the other is the neutral. Green/ yellow ( earths) together. How is it connected at the moment? Due to the nature of your question I really would for safety’s sake, get an electrician to change it.

Did you take a photo of where they went in the old fitting? One set is going to be from the switch, and one is from the loop from another light. You need to know which one is which or be able to test which one is which to ensure you wire it correctly.