The NFL is expected to fine Marshall $5,250 this week for violating the league's uniform rules by wearing green shoes in last Thursday night's game against the New York Giants, a source told ESPN NFL Insider Adam Schefter, and the receiver has vowed to match the NFL's fine with a donation to charity.
During a month in which many NFL players are wearing pink shoes, gloves and wristbands to support breast cancer awareness, Marshall wore green in support of his own foundation, which focuses on mental illness.
Marshall was diagnosed with borderline personality disorder in 2010.
He finished Thursday night's game with nine receptions for 87 yards and two touchdowns as the Bears improved to 4-2 with a 27-21 victory over the Giants.
ESPN NFL Insider Adam Schefter and ESPNChicago.com's Jeff Dickerson contributed to this report.