Here is my list of red things I can think of. Feel free to add any I don't know about. :)
1. strawberries
2. cherries
3. blood
4. red cars
5. healthy lungs
6. red autumn leaves
7. red apples
8. red chili peppers
9. red pens
10. red pencils - colored or regular (colored may be erasable as well)
11. red pears
12. the heart
13. red hair
14. tomatoes
15. salsa
16. red backpacks
17. many countries' flags, in part, like the U.S., Canada, Mexico, Morocco, Malaysia, Kenya, Venezuela, Japan
18. red laptops
19. supergiant stars
20. ketchup