In the beginning, colour light signals were difficult to come by in 3mm scale, but, as the era was 1960s, semaphore was still acceptable. In the long run I wanted a mixture.
The advent of the LED was a godsend and a little searching on the web brought a reliable and trusted supplier in China to the fore.
Suitable supplies of LEDs in red, yellow, green and white have been purchased and along with an American supply of 'targets' (m.a.s., signal heads to you and I) the layout has soon been equipped with full colour light signalling.
The installation of subsidiary signals was made much easier by utilising N gauge items as in the platform setback searchlight signal at the junction. The downscaling isn't as drastic as one might think and only rivet counting will deter you from adopting such practises - the problem with the adamant approach is that projects most times never get finished to an acceptable operational standard!