I think it would be interesting, if changing color is actually the result, to alter the colors to a certain percentage scale around what murder mystery is, with of course the few changes that could come from those percentages being on odd levels. I am going to go into a lot of math so forgive me in advanced. So first, lets begin by taking a look at where the murder mystery color changes fall.
Level 1 (Gray) 0 Experience (0% of the Maximum XP)
Level 10 (Orange) 4500 Experience (Approximately 1% of the Maximum XP)
Level 20 (Yellow) 19000 Experience (Approximately 4% of the Maximum XP)
Level 25 (Aqua) 30000 Experience (Approximtely 6% of the Maximum XP)
Level 30 (Light Purple) 43500 Experience (Approximately 9% of the Maximum XP)
Level 50 (Lime Green) 122500 Experience (Approximately 25% of the Maximum XP)
Level 80 (Red) 316000 Experience (Approximately 66% of the Maximum XP)
Level 100 (Blue) 477900 Experience (100% of the Maximum XP)
Now sure, some of these line up quite nicely like the gray, green, and blue colors at decent milestones. The rest I think can of course be altered game to game to give a nice match to a level. Just to show my idea, I am going to use Treasure Wars as an example since it has the 2nd highest maximum level at the moment.
Treasure Wars Levels Based on Percent Match
Level 1 (Gray) 0 Experience (0%)
Level 10 (Orange) 6750 Experience (1.8%)
Level 15 (Yellow) 15750 Experience (4.2%)
Level 20 (Aqua) 28500 Experience (7.6%)
Level 25 (Light Purple) 45000 Experience (12%)
Level 35 (Lime Green) 89250 Experience (23.81%)
Level 60 (Red) 260100 Experience (69.39%)
Level 75 (Blue) 374850 Experience (100%)
Although I do like this idea, I think it has some flaws. For example, DeathRun seems finalized with the recent update bringing the unlockable costume, but only at Level 40 which is low compared to some of the other games. This would make the color change really small. Same with Just Build, costume is unlocked at Level 20 which would not really fit the system. One solution would be to use only some of the colors, but I think the Level 20 max is great as it is a different color from the rest. Level 40, however, is the same color as Level 30 so that could be changed for improvement.
I also never understood why level 20 and 24 were only 5 levels of orange similiar to aqua when the rest are at least 10. It is like you barely get any time with those level colors before you move onto the next. There is obvious improvement that can be down to improve this. Whether it is changing the level system in Murder Mystery to be wider which would ultimately change the scale for the rest of the games. Here is my final idea, why is a change to every level to make things better and I think it could work as it changes the max level colors for games like SkyWars and DeathRun and Treasure Wars while still keeping the simplicity of the Level 20 games.
My Proposed Global System
Level 1 (Gray) 0% of the Maximum XP in Murder
Level 10 (Orange) Approximately 1% of the Maximum XP in Murder
Level 20 (Yellow) Approximately 4% of the Maximum XP in Murder
Level 30 (Aqua) Approximtely 9% of the Maximum XP in Murder
Level 40 (Light Purple) Approximately 16% of the Maximum XP in Murder
Level 50 (Lime Green) Approximately 25% of the Maximum XP in Murder
Level 75 (Red) Approximately 58% of the Maximum XP in Murder
Level 100 (Blue) 100% of the Maximum XP in Murder