He likes blue. A lot.
For most of my oldest son's first year of preschool (age 4), he wouldn't get dressed for school unless he had a shirt with a picture of a dinosaur.
And at 5...he also liked blue. A lot. All of his school paintings were completely shades of blue as well. I decorated 2 rooms of my house in all blue too. ( I like them. )
He's 6 now. He still likes dinosaurs and the color blue. He also like Legos and Star Wars.
He keeps adding interests and he tends to be passionate about them as they are added. So, based on my experience, I think you have a kid who gets passionate about things. It's a wonderful quality.