Here is a color tip that has been ignored since the very beginning of coin-op parts that were made of plastic or nylon... colors are not always the same, even in parts made by the same mfr at different periods of time. Where this becomes particularly annoying, especially to a die-hard purist, is in control panel push buttons. There were many mfrs over the years & each one had their own formula for colors... reds, blues, yellows & etc, so colors varied wildly among them with no one formula standing out as the "standard". Joystick handle colors varied over the years, as well, but they were usually only a shade or two off when buying the same type from the same mfr & being separated on the control panel made it fairly unnoticeable in most cases. Buttons, being in close proximity, could be real standouts with the color being ever so slightly different. The inconsistency in colors over the years could lead to a control panel that started out with one color of buttons, having as many shades of that color as there were buttons. Today's microswitch pushbuttons are no exception. If you open a case from one batch and a case from a later batch the colors will most likely vary slightly.
So where's the tip? K... if you have one discolored, cigarette burned or broken button on your control panel & there are other buttons of the same color on the panel, you should get them also... even if they are pristine... to make sure that all buttons of that color match. This applies to microswitch pushbuttons, as well. If there is a slight difference in two close batches, then you can imagine how different the color could be if you are changing one from a 1990 game with a button mfr'd in 2007! This isn't the only thing to contend with as colors fade over the years depending upon how much sunlight they have been subjected to, so it's always a good idea to replace all buttons of the same color when one definitely needs replacing.
Color aside, new buttons, not having been banged on for tens of thousands of times, usually make for a better gaming experience.