Users that are supposed to have a colored username in the tab list don't have one. If you take a look at the users "masterchief0707" and "jerkboy2006" you can see that in one picture they have their respective green nametags in the tab list, and in the other their names are the default white color.
MC-73070
Colored Names in Tab List
Resolved
Duplicate
0
Previously reported in MC-73027, closed because unable to reproduce. Can you reproduce this on a 1.8.1-pre1 server and client?