readability of text within coloured backgrounds

Rgb examples of black 000 on cyan 011 then white 111 and then full invert of red 100

Not so easy to read quickly due to the colours 111 011 only been different in red intensity

Over done rgb all inverted might not agree with some that prefer that one colour in the rgb is not inverted

Good Bad Ugly

Red Red Red

Yellow Yellow Yellow

Green GreenGreen

Blue Blue Blue

CyanCyan Cyan

Magenta Magenta Magenta

Green GreenGreen

<span><<span class="start-tag">span</span> <span class="attribute-name">style</span>="<a class="attribute-value">color: rgb(0, 0, 255);</a>"></span><span>Red</span><span></<span class="end-tag">span</span>></span>

<span>Test<br/></span>

Red Red Red

Maybe if the background colour is RGB

then intensity is I=.2989R+.5870G+.1140B

Grey=.5(Black text+White text)

If I use White text else use Black text

Which should make it more readable?

Darkest black on Yellowest Background is best imo