The fact that another cable type works fine doesn't rule out damage to the PlayStation itself. The relevant signal lines are only used for RGB output, so testing with a composite (non-RGB) cable wouldn't reveal the problem.
I'd need more information on what you mean by "an orange tint" to try to guess if that's the only problem, but it at least sounds like the blue line isn't working properly. (Remember that orange is red plus yellow, yellow is made of red and green in RGB, and the PlayStation outputs YPbPr, which would give you a lot more trouble than an orange tint if the green line weren't working.)
If your RGB is using YPbPr over component RCA plugs rather than SCART or some other single-connector solution, I'd see how the result changes if you pull the blue Pb/Cb cable entirely. That won't identify if it's the cable or the console, but it'll test the hypothesis about what's going on, electrically.
As for checking if it's the cable, I'd take a pinout for the AV connector (here's one that uses a photo of the console to show which end should be counted as pin 1) and then, using a multimeter, compare the continuity and resistance of the red, green, and blue lines.
(In a YPbPr RCA cable set, the outer ring is the ground line and the inner pin is the signal, so you'll probably also want to check the resistance of the ground in case something in the circuit has decided to be picky about which return path each color component uses and the ground line for the blue connector is damaged.)
From a quick google, I don't see any signs that the cable should have resistors in there, so if they all show the same resistance (within measurement error) then it's time to examine the PlayStation.
First, check the connector with a light and a magnifying glass to see if there's any damage or corrosion on the relevant pins. (You can get both from the dollar store and, since composite video works fine and you only get an orange tint, you're just looking for whether all the pins are in the same condition.)
Beyond that, open up your PlayStation and check to see if anyone manhandled the connector enough to cause physical damage. Cracked solder joints can be hard to see, so the best solution is to check with a multimeter and not stick the probe directly on the solder blob, but on the connector's lead on one side and something the trace connects to on the other side.
(If it is a cracked solder joint, it's a trivial fix for anyone with a soldering iron. You just reflow the solder.)