Theoretically you can make up as many aspects as you want and they don’t have to look like they do in the UK. And yes by presignals I meant distant signals. Also I know that there are many rules about signals in the real railways but those would just make thing too complicated for a game I think. We could do with a simple logic that with years going new signals would be introduced that would warn trains about signals further away.
I know of two cases where there was fifth aspect made up to use experimentally on a line. One was long long time ago before WW2. The aspect was “yellow over green” and it was put between “green” and “double yellow” aspects. The other case was when some high speed trains were tested in 1988 and a “flashing green” was added which was even less restricting than “green” and allowed the driver to exceed 125 mph.