Throttle,
Trust me, I KNOW what I am talking about!
Blue is a bad light frequency for night vision. It will do you more harm than good. Pilots use "red filtered" lighting to preserve night vision as does BMW, and several other auto manufacturers. The retina does not react well to the blue spectrum of visible light, and will seriously constrict, causing you to have markedly reduced night vision.
I also love the color blau, but not at the risk of having to contend with reduced visibility at night. Blue is on the opposite side of the spectrum from red in terms of visible light! This isn't a disco you're driving, it's a car!
Think of it like this, in terms of optically visible radiation, there are two extremes; Ultraviolet and Infrared...
Keep your vision sharp at night, and if you MUST replace the bulbs, do so with RED ones to help you see better at night! Also, do not look directly at the headlamps of oncoming cars! Divert your eyes to the side of the road furthest from those oncoming lights until the vehicle has passed you.
Night vision is a serious safety consideration!!!!
A dash indicator light, like a high beam indicator, as JCE suggests, is an entirely different matter from the total dash and instrument lighting as I have detailed...
Dig this:
http://www.ncsa.uiuc.edu/Cyberia/Bima/spectrum.html
And:
http://imagine.gsfc.nasa.gov/docs/science/know_l1/emspectrum.html
That should be enough from Bill Nye, The Science Guy for now...
