Firefox keyboard shortcut for Preference | Content | Fonts & Colors

TL;DR :
1. about:config | ui.key.contentAccess = 4
2. new bookmark with Name : 0. whatever & location : about:preferences#content
3. alt-b | 0 to access Preference | Content

Long version
OK, I've been a LONG time firefox supporter, even when they once became 'bloatware' (of sort :D)

BUT it gradually declines personally for me, since the features I most used are slowly being changed / removed, specifically accessing the Preference popup window via keyboard shortcut key

What I used to do was
- Alt-e (Edit menu)
- Preference
- pre-selected Content tab
- Alt-c (Colors... button)
- Alt-s (toggle 'Use system colors')
- Alt-o (for 'Override the colors specified by the page with my selections above:' option)
- A or N (Always / Never option)
- Enter (to save)

It sounds tedious BUT muscle memory makes it pretty efficient & can be done under 2 seconds

This will enable / disable accessibility features, in terms of uniform backgound / foreground colors, which helps to less strain the eyes (with help from some dark theme like solarized / base-16)

Around one year ago, non-ESR Firefox changed the preference window from popup into tabs AND renders the shortcut keys above useless... Which results in me using ESR release (38-ESR to be exact) & enabling incontent option in about:config

Today, for whatever reason, I tried accessing the Colors... button again, BUT with Shift-Alt-C & it works...

I re-read my question on Mozilla Support & finally understand what the answer in the first paragraph meant, you CAN modify Shift-Alt into just Alt... You just need to modify the value of ui.key.contentAccess in about:config from 5 to 4 (the answer has the technical detail of this)

And re-tried the Colors... button & voila!! it works (manly tears of happiness almost shed :D)

faith in Firefox restored & I'm in the main release channel again, goodbye ESR (for now)

Takeaway :
The new steps:
- Alt-b (Bookmarks menu)
- 0 (selects 0. whatever bookmark )
- Alt-c (Colors... button)- Alt-s (toggle 'Use system colors')
- Alt-o (for 'Override the colors specified by the page with my selections above:' option)
- A or N (Always / Never option)
- Enter (saves)