HTML reports are hard to read for colorblind people

[Daimona]

Q	A
php-code-coverage version	7.0.7
PHP version	7.2.2
Driver	Xdebug
Xdebug version (if used)	2.6.1
Installation Method	Composer
Usage Method	PHPUnit
PHPUnit version (if used)	8.3.0

The HTML coverage reports use a red/green combination which is potentially very hard to read for colorblind people. This is exacerbated by cheap monitors with faint colors, where red and green are almost impossible to discern.

Note that red and green are not a problem per se (I actually like the red/green choice), their tonality is.

[sebastianbergmann]

Duplicate of #556.