Can people read it?

Each cell is the row colour as text on the column colour, with its WCAG 2.2 contrast ratio. Ratios are cut, never rounded up: 4.49 is not 4.5.

AAA 7:1 or more: any text AA 4.5:1: body text AA large 3:1: large text (24px, or 14pt bold, about 18.7px) and buttons, icons, borders Fails under 3:1: decoration only

Contrast ratio of each text colour (rows) on each background colour (columns)
Text colour	#F2D50F	#121212	#12B89A	#2D55FF
#F2D50F	same colour	12.75:1AAA	1.71:1Fails	3.70:1AA large
#121212	12.75:1AAA	same colour	7.44:1AAA	3.43:1AA large
#12B89A	1.71:1Fails	7.44:1AAA	same colour	2.16:1Fails
#2D55FF	3.70:1AA large	3.43:1AA large	2.16:1Fails	same colour

Best pairs for text

Every pair that reaches 4.5:1, strongest first, with plain white and near-black added as candidates.

#121212 + #FFFFFF 18.73:1 AAA
#121212 + #F2D50F 12.75:1 AAA
#121212 + #12B89A 7.44:1 AAA
#2D55FF + #FFFFFF 5.44:1 AA

Contrast is one part of accessibility, not all of it. RiotPad checks colour pairs against WCAG 2.2; it does not certify a website as accessible. Ratios use the WCAG 2.2 relative-luminance formula (Success Criteria 1.4.3, 1.4.6 and 1.4.11).