hints kitten: Workaround for some broken light color themes that make the hints text color too low contrast to read

Fixes #7330

tools/utils/colors.go

@@ -0,0 +1,21 @@
+package utils
+
+import (
+	"fmt"
+)
+
+var _ = fmt.Print
+
+func RGBLuminance(r, g, b float32) float32 {
+	// From ITU BT 601 https://www.itu.int/rec/R-REC-BT.601
+	return 0.299*r + 0.587*g + 0.114*b
+}
+
+func RGBContrast(r1, g1, b1, r2, g2, b2 float32) float32 {
+	al := RGBLuminance(r1, g1, b1)
+	bl := RGBLuminance(r2, g2, b2)
+	if al < bl {
+		al, bl = bl, al
+	}
+	return (al + 0.05) / (bl + 0.05)
+}