Supporters of an effort to replace Colorado’s flat income tax with higher taxes on wealthier individuals say they’ve collected over 157,000 signatures to get the measure on the November ballot. Under those changes, a household making $1 million annually would pay $15,925 more in income taxes, according to the coalition’s calculator. Supporters of a graduated income tax proposal rally outside the Colorado Capitol on March 17. Advance Colorado delivered nearly 190,000 signatures, which are under review, to place its countermeasure capping the state’s income tax rate on the November ballot. If approved this year, the graduated income tax measure would be one of the most seismic changes to Colorado’s tax policy since TABOR’s enactment more than 30 years ago.