I can certainly understand and support the design choice of making the laser colors confirm to the actual scientific colors of the temperatures involved as it adds a note of forethought and realism to the design.
But it's also a game, where the ease to distinguish these differences in laser modes becomes slightly more important. And like DarkwingDiva here, I've been having a hard time telling apart laser levels while playing in-game myself, usually not realizing just what laser level I was actually at until several moments too late, and have been overall unclear just how many laser levels DU offers presently as a result. It's not an especially big problem yet, because in the flurry of multiplayer gameplay, the details doesn't matter so much as long as you've got weapons to fight back with, and they enable you to do more damage to the opposing player quicker than they can to you.
But as we look ahead to singleplayer gameplay in the hopefully not too distant future, it does occur to me that a bit better distinguishing between laser level colors would be helpful. At the moment, they're all a little too close together in terms of color, making it hard to visually tell them apart unless you look closely. DU wisely compensates by having the shape of the actual "bolt" fired vary from laser level to laser level...but I've found that in practice this only goes so far.
A part of me would want the laser levels restored to their classic colors then, if only for continuity between games. But since a degree of realism is apparently desired at any rate, I have a suggestion that might help; have the color of the lasers be determined not by the temperature they're burning at, but rather the type of plasma matter used in the laser bolts that are fired in each laser level.
Allow me to explain; in the D1 opening briefing, the MD notes to himself some of the weapon specs his Pyro-GX was being equipped with, and notes that it was equipped with argon-based lasers, presumably laser level 1, since that was the default starting laser level of the time. That suggests to me that laser level 1 fires bolts of energy that are in some way fueled by the gas argon. Likewise, the D2 robot briefing for the PIG robot (red guy that fires laser level 6) is noted to fire xenon-based lasers, suggesting laser level 6, unlike level 1, uses xenon as a key element in the bolts fired. All of this likely referencing how real-life lasers will use some of these same gases as part of their function, and there are real life argon-ion and xenon-ion lasers, though not functioning quite like portrayed in Descent, obviously.
But these gas when charged into a plasma will give off a glow discharge and produce unique colors--basically it's the same principle of how a neon light works; gas when given an electric charge puts off a specific color, often unique to that element, depending on how pure the sample is. This is what I had always thought was why Descent's laser levels had such diverse colors personally; not because of temperature, but because of what gases they were fueled with manifesting these colors. And since you can actually get a whole wide array of colors, including all of the colors past Descent games used for laser levels, fairly readily, I figure the developers can use this trait to justify different laser colors.
But I would recommend reading up on what chemicals produce what colors if you were to do this, more that the original Parallax team did at least. For instance, argon does not put off the red color of laser level 1 but rather a more lilac purple color (actually very akin to laser level 2). But associate the right chemicals with the right laser levels, and you're good to go.
Here's a quick example list:
-Red lasers: neon-based
-Purple lasers: argon-based
-Blue lasers: mercury vapor-based
-Green lasers: krypton-based (but apparently green is only produced in certain conditions, otherwise an off-white is more likely)
-Yellow lasers: sodium vapor-based
-Blue-white lasers: xenon-based
Further details of the effect I'm talking about, and a list of gases and the colors they can produce.