There are two instances (details) in the text that can support this idea. First, when Anna and Olivia discuss their different points of view regarding oil paintings. Anna argues that she would like to use color and the oil paints instead of charcoal; however, Olivia does not like the idea of using oil paintings, since charcoal allows her to erase something if she makes a mistake. Second, towards the end, Anna says "I'll never have a charcoal life. Mama sees the world in colors too!". With this statement, Anna explains that she and her mother see the world in a particular way, in this case in color. Therefore, she implicitly states that there are different ways of seeing or perceiving the world.
This sentence shows Algernon's doubts and critics about marriage.
Through this passage we can see that Algernon does not believe that husband and wife can be faithful to each other, and that they always need a third person to keep them satisfied.
