A: "Dude! Have you ever wondered if what I see as 'red' is the same color that you see as 'red'?"B: "No dude! It's scientific. 'Red' is just a label for a certain wavelength on the spectrum."A: "I know, Dude. But how do we know what our brains 'see' when our eyes perceive that wavelength? Maybe what I call 'red' is what you see when you say 'green.' We'd never know because we always call the same color 'red' or 'green' when we see it. But what color are we ACTUALLY seeing?"B: "Dude..."Have you ever had THAT conversation before (with or without the ubiquitous use of "dude")? That's exactly what this post is NOT about.Before I go on, I'd like to announce that I am deeply in like with my new iPhone 5s. I've only had it for a little over a month, but I finally know what all the fuss is about (it's my first zhìnéng shǒujī 智能手机 ever).Naturally, one of the first apps I got was Pleco (coming soon: a post about why I love Pleco). One of the options that was on by default was the "Tone Colors." (If you're not familiar with what tone colors are, please see John Pasden's review of  Chinese Through Tone & Color by Nathan Dummitt.)I love tone colors, and left them on in Pleco. But the problem (as John and his commenters discuss) is: What's the biāozhǔn 标准? What colors should be assigned to each tone?Here's a summary of what 4 people think: [updated to include Hanping]

According to Pleco's creator Michael Love, Pleco first introduced tone colors in Pleco 2.0 Beta 1 (October 2007). Drummitt's book came out six months later in March 2008, and then MDBG added tone colors a year later.Right now, I'm an avid user of MDBG and Pleco. But the tone colors don't match. I don't want to discuss what the "right" colors for each tone should be, I just want it to be consistent. But I've found that people feel very strongly about "their colors." And I think a consensus is impossible to reach.But no problem. Pleco has set an example of how apps should handle this issue. Look at the option in Pleco's Settings > Colors > Configure colors > Tone 1 color:

That's the solution! Just let everyone set their own tone colors. Since MDBG doesn't offer this option (yet), I'd have to set Pleco's colors to match MDBG's. UPDATE:MDBG now offers Pleco's colors as one of the options (see here).(Note: the Pleco colors are in HSB by default, but if you touch the number itself you can toggle through RGB or Hex.)I hope all you who are developing apps that include tone colors will follow Pleco's lead on this: go ahead and pick your favorite defaults (Michael Love said "I believe the (Pleco) colors were originally chosen based on what colors of pen the friend of mine who came up with it had available"), but please PLEASE let us users customize them.UPDATE:Hanping has a big preset menu to allow users to choose their favorite color schemes (but I don't know what some of those presets are).