Bell peppers are a vegetable, and I like bell peppers of all colors, although I do prefer the red ones. The part of the bell pepper that we consume encloses the seeds. As far as I know, people don’t eat bell pepper seeds.
The spice that is pepper (black, white, green, etc) is the seed from a fruit. There is only one seed per flower.
On a completely unrelated note, in Japanese, the bell pepper is called piman, and to call someone that is a big insult. The reason is what do you get when you cut a bell pepper in half? Air, lots of air. So to call someone “piman desu” is to call them an air head! I love that little bit of trivia!