I would say the pic's the guys posted are the correct gold, I had a gold K0 back in the day. Your pictures looked really yellow, that said one of them did kinda look gold, so like others have said you would really have to see it. $4,500 sounds like a good price for a K1 but like 754 said it now comes down to condition, status of motor, etc. I always get impressed when the seller shows me a bunch of receipts, maybe a journal of everything done. I also look at his/her shop and how well things appear to be handled/organized, etc.
Another telling thing is going to be the difference in engine and frame serial numbers and to ensure the serial numbers are in the K1 series. There is also a thousand different things, OK maybe 100 different things that make it a K1 versus a newer CB750, a Franken bike would have much less value. You can arm yourself with allot of these facts before going to see the bike.