diff --git a/uppsrc/Core/src.tpp/Color$en-us.tpp b/uppsrc/Core/src.tpp/Color$en-us.tpp
index c6944f501..91579fd1a 100644
--- a/uppsrc/Core/src.tpp/Color$en-us.tpp
+++ b/uppsrc/Core/src.tpp/Color$en-us.tpp
@@ -305,6 +305,14 @@ olor][@(0.0.255) `&]_[*@3 c])&]
 [s2; Converts a color [%-*@3 c][%-  to grayscale].&]
 [s3; &]
 [s4;%- &]
+[s5;:IsDark`(Color`):%- [@(0.0.255) bool]_[* IsDark]([_^Color^ Color]_[*@3 c])&]
+[s2; True if [%-*@3 c] grayscale level is lower than 80.&]
+[s3; &]
+[s4;%- &]
+[s5;:IsLight`(Color`):%- [@(0.0.255) bool]_[* IsLight]([_^Color^ Color]_[*@3 c])&]
+[s2; True if [%-*@3 c] grayscale is higher than 175 (255 `- 80).&]
+[s3; &]
+[s4;%- &]
 [s5;:StraightColor`(RGBA`):%- [_^Color^ Color]_[* StraightColor]([_^RGBA^ RGBA]_[*@3 rgba])&]
 [s2; Converts a RGBA structure [%-*@3 rgba] to a [* Color].&]
 [s3; &]