I recommend choosing colors you like, and then adding accent pieces that are inexpensive, and can be easily switched. My classroom has had a teal/aqua/turquoise (umm, could someone please tell me the difference please?), for the last 4 years, and I love it! It's one of my favorite colors. My boarders are black with white polka dots, and teal and white chevron. There are splashes of hot pink, lime green, yellow, purple, and orange.
This year, I decided to make my own decor items, which you can find in TpT store. I wanted something that went along with the colors I love - it's a collection of various "Chevron Brights" (teal, hot pink, lime green, yellow, purple, and orange) items like supply labels, classroom library labels, alphabets, team signs, calendar cards, shapes, word wall cards, numbers, hall passes, etc...
As teachers start coming back to work in their classrooms, there inevitably are shelves, tables, chairs, desks, supplies, and so on that teachers don't want anymore. Usually, teachers put this stuff in the hallways with signs on them indicating they don't want them anymore. See something you like or need? ASK that it is in fact up for grabs, and then get it to your classroom. Also, my school places supplies that are up for grabs in the teacher work room. If you don't have one at your school, start one! You'd be surprised what will wind up on that table!