Forza Horizon 4

All of the "Event" Brick Challenges are the lego blocks that are the blue color. They include all of the races, Hype Tour and the championship races like the LEGO Goliath and the final Speed Champions race. You get 20 blocks for completing each race and 40 for winning each race. The final Speed Champions race won't unlock until you get 11,500 of the gold legos from doing everything (completing all of the other colors). Once you have completed everything, win the final Speed Champions race and you will be rewarded with the achievement as well as a statue for your LEGO house.