It expresses that the people are working together to make a more perfect union and make the United States of America a legitimate country with a constitution. The people in power are chosen by the general population, so it's a form of representative democracy.
24 colour tiles because if you convert 3/4 to a percent, it is 75%. 75% of 32 is 24 (After converting the percent to a decimal -> 32 x 0.75 = 24) Sorry if this sounds confusing.
