USE ALREADY EXISTING RESOURCE
Particularly, DESIGN SEEDS
Just a few examples to show you the color palette I used. There are literally millions, maybe even billions of existing color palettes out there, the combinations are endless! So I don't see any reason why we shouldn't utilize them. And of course, HOW you use them is very important too. Unfortunately, my only tip for you is CONTRAST. Learn how to use it to your advantage, practice makes perfect!
Also, you don't need to strictly stick to the color palette you chose. Making some minor changes to the shade may be permitted, as long as it makes your design look good. ;)
So that's it, this is my last post on how to do 'Subway style' typography art. I hope you learned something from me to improve on your own design skills.