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Default colors should be replaced when +theme_blackboard() is added to ggplot object
A suggestion: the default color for lines, points, etc. should be changed to white as part of the theme_blackboard, theme_abyss, etc. themes that have a dark background.

Really wish this PR would get merged into ggplot2... https://github.com/tidyverse/ggplot2/pull/2749
Check out {thematic} package: https://rstudio.github.io/thematic/