In which sentence is the colon used correctly?

A. Mark Rothko, another modern master, asserted: "There is no such thing as a good painting about nothing."
B. Van Gogh said that: "a good picture is equivalent to a good deed," an intentional and conscious action.
C. When we see an amazing painting by a toddler: we wonder at the incongruity.
D. Great paintings are great and powerful ideas: often new, even revolutionary.