That's one of the reasons why we use IEC colors for mains inside of our equipment, even though we're building it in the US and largely for the US market and it mostly gets serviced by us rather than end users or third party technicians. This is a problem with the US system using Green for PE and Red for phase, given how common red-green color blindness is. Well, really, you shouldn't rely on color alone at all, but comprehensively marking wiring is a level of effort typically only justifiable in things like industrial cabinets. Another thing to consider is that serviceable wiring, whether inside of equipment or facility wiring, should not rely on easily confused colors for differentiating conductors that do or do not carry hazardous voltages.

In single phase systems in the US, red is used for the second line conductor in 240V circuits and is also sometimes used for switched mains conductors, so there's some parallel there for using it for a similar purpose inside of equipment. It wouldn't be unreasonable to use those colors for additional lines carrying mains voltage inside of an appliance where needed. In the US, Black/Red/Blue are used for each of the three phase lines in 120V/208 systems, and in IEC Brown/Black/Gray are used. Yes, it doesn't really matter all that much inside of equipment unless you have particular standards to meet that tell you otherwise, but NEC (US), IEC, and other standards define additional colors to support three phase wiring. Power supplies in PCs have standard wire colors (as per ATX spec) For example DC power uses red and black, or USB has specific wire colors by standard. But for some things color coding standards do exist so its best to follow them to make things easier to understand for people. So its impossible to make a certain color code be required by law. Also typically the inside of equipment is serviced by someone who is specifically familiar with that type of equipment. So we just don't have nearly enough colors to color code all of that. Some wires might carry AC power, some DC power, some might be switched power for some sort of load, some might be digital signal lines, some might be 24V signal lines, some might be analog lines, some might be digital communication buses. But when it comes to the inside of equipment, they are much more complex than an electrical cabinet. Not having a standard would make that a living hell to sort out what is what. They commonly open up a junction box and just find a mess of wires inside coming in from all directions. The standard mains color codes are there to help electricians wire things up correctly.

Transformer color codes 3 wire