Border colors for Table tool in the Atto HTML editor lack sufficient color contrast with the default background color. These table border colors are the same colors that the fontcolor plugin uses. See MDL-52391.

WCAG 2.0 level AA requires a contrast ratio of 4.5:1 for normal text and 3:1 for large text (18 point or larger). Level AAA requires a contrast ratio of 7:1 for normal text and 4.5:1 for large text. See WCAG 2.0 Guideline 1.4.1.

Current contrast ratios:
Red contrast ratio: 3.75:1 (fails level AA and AA for normal text; fails AAA for large text)
Yellow contrast ratio: 1.48:1 (fails level AA and AA for normal text; fails AA and AAA for large text)
Green contrast ratio: 1.48:1 (fails level AA and AA for normal text; fails AA and AAA for large text)
Blue contrast ratio: 1.48:1 (fails level AA and AA for normal text; fails AA and AAA for large text)

These colors are in conformance with the Web Content Accessibility requirements at the AAA Level:

• Red: #a20000
• Green: #006000
• Blue: #004d83
• Purple: #800080
• Magenta: #980068
• Gray: #3c3c3c

Tests were conducted with the Paciello Group’s Colour Contrast Analyser and with WebAIM’s Color Contrast Checker.

See the attached document for additional color recommendations.