What colour are the headbox lights on a British Rail diesel?

I am currently re-configuring the British Rail diesels on my game with the correct horn and engine sounds, and engine specs, after discovering these items were wrong originally.

One piece of the jigsaw has stumped me at present and that is the colour of the headbox lights on the BR Class 37's, 47's, 50's, 20's and 55's - and that is what colour light should I have on the headbox lights?

Are these headbox lights portrayed as yellow colour or white colour on the prototype locomotives?

Not quite sure I follow this question. Do you mean the headcode boxes? If so, then they were lit with white light, albeit, quite dimly. The same was the case when the headcodes were replaced by the white dots.

However, I'm fairly certain that the BR locos (or the vast majority of them, certainly the tmz06003 55s) should already have the correct specs though there are a number of engine sounds that aren't available.

I think it would have changed over the time. When the headcodes were in use between c1960-1976, it would have been tungsten light bulbs. These give out a soft orange-yellow light rather than a hard white light. The same type were used in most Mark 1 coaches before they were refurbished e.g. http://neiloseman.com/wp-content/uploads/2013/08/stockvault-bulb128619.jpg

As time went on it's probable that bulbs which gave a more white light were used, but that would likely have been after the headcodes had been wound back to 0000 or changed to domino style.

I'd disagree with you there. From memory, I recall a warm yellow glow eminating from the domino lights. I remember thinking (in the days before I knew any different) that they must be next to useless at night!

You may well be right, the ole memory ain't what it used to be. I suppose all I'm saying is that tungsten was all there was to start with, but by the 1980s there were brighter whiter bulbs available, which may well have been used. A lot of the mainline passenger locos got sealed beam pretty quickly after headcodes were defunct - the Deltics were mostly done by mid 1978 for instance.

Sorry, didn't mean to sound brusk there.