Sea ice colormap set_under color #1082
Description
The cmap set_under color is none in some mpas-analysis sea ice plots https://web.lcrc.anl.gov/public/e3sm/diagnostic_output/ac.dcomeau/E3SMv3_dev/20250327[…]pas_analysis/ts_0001-0040_climo_0031-0040/sea_ice/index.html