Margot is trying to tell everyone that the sun is round like a penny and shines so bright. It brings blonde to your hair and blue to your eyes. Nobody is believing her and are about to punish her for it.
Coming from rain and gloomy weather on Venus, the kids don't believe Margot when she talks about the sun. The differences between Venus and Earth is apparent and the jealousy towards her. The sun is bringing her into conflict.