colors: remove colors that aren't AA accessible

per https://webaim.org/resources/contrastchecker/

common/colors.go

@@ -26,8 +26,6 @@ var Colors = []string{
 	"beige",
 	"bisque",
 	"blanchedalmond",
-	"blueviolet",
-	"brown",
 	"burlywood",
 	"cadetblue",
 	"chartreuse",
@@ -35,29 +33,19 @@ var Colors = []string{
 	"coral",
 	"cornflowerblue",
 	"cornsilk",
-	"crimson",
 	"cyan",
 	"darkcyan",
 	"darkgoldenrod",
 	"darkgray",
 	"darkkhaki",
-	"darkmagenta",
-	"darkolivegreen",
 	"darkorange",
-	"darkorchid",
 	"darksalmon",
 	"darkseagreen",
-	"darkslateblue",
-	"darkslategray",
 	"darkturquoise",
-	"darkviolet",
 	"deeppink",
 	"deepskyblue",
-	"dimgray",
 	"dodgerblue",
-	"firebrick",
 	"floralwhite",
-	"forestgreen",
 	"fuchsia",
 	"gainsboro",
 	"ghostwhite",
@@ -67,7 +55,6 @@ var Colors = []string{
 	"greenyellow",
 	"honeydew",
 	"hotpink",
-	"indigo",
 	"ivory",
 	"khaki",
 	"lavender",
@@ -98,7 +85,6 @@ var Colors = []string{
 	"mediumslateblue",
 	"mediumspringgreen",
 	"mediumturquoise",
-	"mediumvioletred",
 	"mintcream",
 	"mistyrose",
 	"moccasin",
@@ -119,26 +105,19 @@ var Colors = []string{
 	"pink",
 	"plum",
 	"powderblue",
-	"purple",
-	"rebeccapurple",
 	"red",
 	"rosybrown",
-	"royalblue",
-	"saddlebrown",
 	"salmon",
 	"sandybrown",
 	"seagreen",
 	"seashell",
-	"sienna",
 	"silver",
 	"skyblue",
-	"slateblue",
 	"slategray",
 	"snow",
 	"springgreen",
 	"steelblue",
 	"tan",
-	"teal",
 	"thistle",
 	"tomato",
 	"turquoise",