I recall reading some WW2 air combat stuff, where the pilot asked the ground personnel to load the belts with every fifth with tracers. That leads me to believe the pilot could affect the density of tracer rounds - or even leave them away if he felt like a really good shot.
About the colours: IMO WW2 colour films weren't too accurate in colour reproduction and the bygone 70 years certainly have had an affect to the originals even before they started to transfer them to first magnetic, then digital formats. Add to that, that there was and still is several types of films which act differently by their very nature. Some are vivid, some flat, some tend to overexpose certain hues to warm or cold/red or blue. Heck, even my monitor has a bunch of presets like "photo", "movie", "standard" etc. With all these variations you really can't tell the real colour until you've seen the real stuff. Even then your senses may lie, making you believe an enhanced picture is the most life-like.