@Leskunk
Hi there,
Assuming you are refering to the webversion of OSM: some pages are hidden after the last match of the season has been played. You can still go to that page by typing in the correct url. If you want to keep training your players then you have to type in Training after the / (slash) in the url.
If you are refering to the outline of the players:
Green = player is placed on the exact same position as his favorable position (an LW is placed on the LW position)
No outline = player is placed on the correct line but not on his favorable position (an RM is placed on the CM position)
Red = player is placed on the wrong line (a midfielder is placed on any of the offensive positions, defensive positions or as a goalkeeper)
If you are refering to the backgrounds:
Blue = normal
Blue/Gold = World Star (100+ rating)
Black = In Form player