The bus operator with which I've ridden the most has been a company called Trentbarton. Since I've been in Nottingham, I've used their buses on all occasions except for two (the college bus to London and an independent bus operator during my first visit to Hucknall).
I've ridden three of Trentbarton's routes; here are pictures of the bus interiors of said rotes:
recently avoided a collision. The only Two bus I've observed so far has been yellow.