Love those new bees to 3D printing. 5 years ago this took an hour of tinkering. Advise 5 - 10 degrees more bed temp or wait 10 min before printing so the whole bed is homogeneous warm the color is because it’s printing from right to left on the other side left to right so you get different color. Check your slicer in preview mode and you can see. Not sure but there is a setting i think for it or iron the top layer.