@cwilcox808 @AmeliaBR So <mark> itself is not accessible by default? The lightest gray that has at least 3:1 to yellow is #8f8f8f, a fairly dark gray, which means that <mark> on any page in light mode (white background or similar) has less than 3:1.
Base Color : E19F68
Mode : monochrome-light
#656565
#737373
#818181
#8F8F8F
#DE985C
#E4A674
#E9B58B
#EEC4A2
#F2D4BA
Base Color : 2807D8
Mode : monochrome-dark
#13055A
#180679
#1E0798
#2408B7
#2909D6
#7F7F7F
#8F8F8F
#9F9F9F
Base Color : F6B0C6
Mode : monochrome-light
#808080
#8F8F8F
#9F9F9F
#EE7198
#F28DAD
#F5A9C1
#F9C6D6
#FCE2EA
Base Color : 33DCB5
Mode : monochrome-dark
#177962
#1B9176
#1FA989
#22C29D
#27DAB0
#8F8F8F
#9D9D9D
#ABABAB
#B9B9B9
Base Color : F8C9C4
Mode : monochrome-light
#808080
#8F8F8F
#9F9F9F
#ED7D71
#F1978D
#F5B1A9
#F9CBC6
#FCE5E2
Base Color : F987B6
Mode : monochrome-light
#808080
#8F8F8F
#9F9F9F
#F669A3
#F887B5
#FAA4C8
#FCC2DA
#FEE1ED
Base Color : 1025E3
Mode : monochrome-dark
#0A136A
#0C1884
#0E1C9F
#0F20B9
#1124D4
#818181
#8F8F8F
#9D9D9D
#ABABAB
Base Color : A77B1B
Mode : monochrome-dark
#382A0A
#58410F
#775814
#976F19
#6A6A6A
#7C7C7C
#8F8F8F
Base Color : FA9EB8
Mode : monochrome-light
#808080
#8F8F8F
#9F9F9F
#F56991
#F887A7
#FAA4BD
#FCC2D3
#FDE1E9