(excerpt from the rules)
§7.05 Startcrash-rule: The causer of a startcrash gets one yellow. In addition the driver has to omit the qualification of his next race of the cup. Very hard offences can be punished with two yellows.
§7.06 The EOLC-theory of colors: If you have treasured 3 ore more yellows in a cup, you will be banned from the next race. All yellows will be deleted except 2. For each race without a yellow, one yellow will be deleted.
§7.07 Disqualification: If you get 3 yellows in one race, you will be disqalified afterwards. Despite this, a very hard offence, reckless or very careless driving can result in a qualification as well.