Contrast comparisons

A color of rgb(100, 100, 100) on black has a luminosity contrast ratio of 3.550595556268441, falling short of both Level 2 and Level 3. When enhancing contrast and having such similar colors, it actually lessens the readability.

A color of rgb(150, 150, 150) on black has a luminosity contrast ratio of 7.2236099811596866, which meets Level 2, but falls short of Level 3. Enhancement at this level sharpens the letters more than increasing the contrast between the text and the background.

A color of rgb(200, 200, 200) on black has a luminosity contrast ratio of 12.719459678993227, which exceeds Level 2 and Level 3. Enhancement at this level also sharpens the letters.

Side note: I kind of wish I had found the Colour Contrast Analyser Firefox Extension before writing the "High Contrast Design" section of the chapter.