Please answer the following question: I want to test the ability of students to read a passage and answer questions about it. Could you please come up with a good question for the passage "Debate remained limited, and major decisions regarding the economy and defence were avoided or dealt with cursorily; the GPC largely remained "a rubber stamp" for Gaddafi's policies. On rare occasions, the GPC opposed Gaddafi's suggestions, sometimes successfully; notably, when Gaddafi called on primary schools to be abolished, believing that home schooling was healthier for children, the GPC rejected the idea. In other instances, Gaddafi pushed through laws without the GPC's support, such as when he desired to allow women into the armed forces. Gaddafi proclaimed that the People's Congresses provided for Libya's every political need, rendering other political organizations unnecessary; all non-authorized groups, including political parties, professional associations, independent trade unions and women's groups, were banned."?
A:
Blue, red, and yellow are considered in the field of art to be what kind of colors when combined in various amounts to produce other colors?