Anything goes with dark blue really. I love bright colours. And pattern.
We've just got a new sofa too, which is on the lighter end of forest green and have redone the living room. We have an existing navy blue armchair, which isn't ideal but has to stay for the moment. We switched out our black tv unit for an oak one, and it looks much better.
In terms of adding colour, I've used cushions, curtains, throws, rug, footstool, potted plants in pretty planters, a bunch of brightly dyed dried flowers, light shades. Basically anything that can be changed relatively cheaply and quickly if I get bored of it. I shop on a budget and picked up lots of things from Dunelm and various online shops. New TV unit was from Daals.
In terms of your tv unit, I don't think a dark wood is the way to go. Something lighter to contrast with the dark sofa would look better.
If you like colour, then add it! I think colours would look great with your new sofa!
Use Google images to see how other livings rooms with blue sofas have been styled.
Happy lounging!