Colors inside DIN 5 (MIDI) cable
I made on my Arduino Uno some MIDI in/outs, but never seen some color scheme.

The MIDI ports have specific numbers (which are not so intuitive). And also check good what is the front and back.

Btw, MIDI is far from obsolete. Every synth still uses them (although USB MIDI is getting more popular, a lot of music devices with with DIN5 MIDI plugs). MIDI cables can be found at every decent music shop.