Gmapping map has mixed colors

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As shown in the following picture, the resulting map produced by gmapping has mixed color dots. I have only seen gmapping producing maps with black dots for occupied grid, but not with these many colors. Is this normal behavior? If not, what might be wrong?

I am playing a rosbag file, which publishes laser scans, odometry, tf transforms and time (to /clock since I am using use_sim_time). I have much more (2 times) odometry messages than laser scan messages.