What color curtains should i buy for my apartment?

you can add any color with beige cause it is a neutral color. reds, blues yellows etc..

My suggestion. find a throw rug and some pillows for the couch and match the curtains with those. It's not so much work but it will really add a lot.

I have a lot of beige in living room, great room if you will, and an open arch into kitchen.  It has a green range.  So, easy choice for accent color.  I went green.  Besides, it's easy to find green accessories.   Try basing your color scheme on the same kind of idea ~ easy to find & color already somewhere else in house visible from that room.  It worked well for me.