1. What are score of a clan and score of a player and how is it obtained?

Score of a clan is sum of scores of all its members. It should represent a 'power' of a clan in terms of number of top tier vehicles. Score of a player is calculated as follows:
Score formula
∑: denotes summation over all player's tanks.
Si: is base score: 1000 for tier 10 heavys and mediums, 900 for tier 10 TDs and tier 8 artys. 0 for all other vehicles.
Wi: winrate percentage on current tank.
Bi: battles played on current tank.
WN7: player's WN7 rating.

2. What is rating color scheme based on?

Bottom 10% of players. 10% - 45% 45% - 80% 80% - 95% 95% - 99% Top percentage (1%).

3. What is an efficiency and WN7 rating of a player?

Efficiency rating is popular rating formula obtained same as here. WN7 is another popular rating system. You can find out more here.

4. Other questions?

If you have any other questions mail me at andrej.hoos@gmail.com or post in this topic.