How do you change the opacity of highlight colors in Preview?

Apple has programmed these colors into the Preview application. You cannot alter them, or their opacity.

If you were to use a proper PDF viewer like Adobe Acrobat Reader DC, then you would have complete control over your specific highlight color, and opacity. You simply highlight text, and then right-click on that highlight and choose Properties…

Until Sierra the highlighter tool in Mac OSX was near-perfect and was sufficiently transparent that it did not interfere with the text being highlighted. For reasons that only Tim Cook could explain, it was altered and now the highlighting is dark enough to obstruct the text highlighted defeating the purpose of highlighting.

My solution is to go to take my pdfs to my 2 Snow Leopard Macs and highlight in the preview, when it used to function as one would expect. ... Maybe even install a pre-Sierra Mac OSX on a VM (through Virtual box) to get access to an earlier version of Preview that did not adversely highlight text ... just a thought