I can sneak up on you or be right in front of you without you knowing. But when I reveal myself you will never be the same. Who am I?

What type of celebration do the colors in manet’s painting suggest, in contrast to gauguin’s? masked ball at the opera by edouard manet courtesy national gallery of art, washington. breton girls dancing, pont-aven by paul gauguin courtesy national gallery of art, washington search each photo up who ever answers it gets 20 points.