Picasso went through many periods in his life. One of the most famous ones was the Blue period(1901-1904).
During that period his friend died which encouraged him to paint in very sad colors.
After that was the Rose period(1906-1907).
In this period he painted with reds and other bright colors. His paintings were positive.
When he got older, he painted with a circus theme. Some of these paintings were Parade and Acrobat with ball.
Picasso had very many moods when he painted, which probably caused these periods.