How are they similar?

Answer: One of the similarities that both, the Mona Lisa and the self-portrait with monkey by Frida, is that both of the paintings were made with oil. Both paintings are self-portraits of either themselves or someone else.
Answer:
Some ways these two paintings are similar are they are both portraits of humans. One is a painting of a women painted by Leonardo Da Vinci, and the other is a self-portrait by Frida Kahola. They both have lighter colors and Frida is known for her passion and bold colors. Leonardo creates shadows and colors as well. They both make the skin glow. Both realistic portraits as well.
Hope this helps! Sorry if it didn't. :')
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