Millions of dollars are flowing into November’s election in an effort to sway Coloradans’ vote on two ballot measures related to the state’s income tax system. Supporters of Amendment 87, which would replace the state’s flat income tax with a graduated system, had disclosed around $1 million in spending as of the Oct. 6 filing deadline with the Colorado Secretary of State’s Office. The Amendment 87 campaign received small donations between $5 an…