Fix plot_reflections

[rjgildea]

Don't plot white circles with white edges on a white background.

[codecov]

Codecov Report

Merging #1346 into master will increase coverage by 0.10%.
The diff coverage is 94.44%.

@@            Coverage Diff             @@
##           master    #1346      +/-   ##
==========================================
+ Coverage   64.22%   64.32%   +0.10%     
==========================================
  Files         616      616              
  Lines       69811    69806       -5     
  Branches     9536     9536              
==========================================
+ Hits        44834    44906      +72     
+ Misses      23211    23113      -98     
- Partials     1766     1787      +21     

Impacted Files	Coverage Δ
command_line/plot_reflections.py	61.01% <92.85%> (+61.01%)	⬆️
test/test_plot_reflections.py	100.00% <100.00%> (+55.55%)	⬆️

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[Anthchirp]

looking good. I'll add a commit to update the test though