Starfleet uniform

Why do the starfleet crews on the cerritos and some other ships wear the newer uniforms (Early 2380s), while some other starfleet crews wear the older uniforms (2370s-Early 2380s)?

Here are pictures of characters in uniforms from different series that I found online. It really gives a different and interesting perspective on the characters. What do you think?

Why is Kirk shirt in the same scene in TOS the changeling either gold or green, depending on the recording source, and which one is the correct original one? The color is so different, that it can't be explained away by slightly different color representations on different screens.

How would you rank your favorite starfleet uniforms?

I'd rank them, from most to least favorite:

1. VOY

2. DS9 (seasons 1-3)

3. TOS

4. TOS (movies 2-6)

5. TNG (season 3-7)

6. PIC

7. ENT

8. DS9 (seasons 4-7)

9. TNG (seasons 1-2)

10. TOS (the motion picture)