diff --git a/README.rst b/README.rst
index 02429962..d01188e3 100644
--- a/README.rst
+++ b/README.rst
@@ -168,4 +168,4 @@ RGBGFX generates palettes using algorithms found in the paper
 (`GitHub <https://github.com/pagination-problem/pagination>`__, MIT license),
 by Aristide Grange, Imed Kacem, and Sébastien Martin.
 
-RGBGFX's colour palette was taken from `SameBoy <https://sameboy.github.io>`__, with permission and help by `LIJI <https://github.com/LIJI32>`__.
+RGBGFX's color palette was taken from `SameBoy <https://sameboy.github.io>`__, with permission and help by `LIJI <https://github.com/LIJI32>`__.
diff --git a/src/gfx/reverse.cpp b/src/gfx/reverse.cpp
index 15a08c89..3f09f75a 100644
--- a/src/gfx/reverse.cpp
+++ b/src/gfx/reverse.cpp
@@ -141,7 +141,7 @@ void reverse() {
 	std::vector<std::array<Rgba, 4>> palettes{
 	    {Rgba(0xFFFFFFFF), Rgba(0xAAAAAAFF), Rgba(0x555555FF), Rgba(0x000000FF)}
 	};
-	// If a palette file is used as input, it overrides the default colours.
+	// If a palette file is used as input, it overrides the default colors.
 	if (options.palettes.has_value()) {
 		File file;
 		if (!file.open(*options.palettes, std::ios::in | std::ios::binary)) {
diff --git a/test/asm/test.sh b/test/asm/test.sh
index 14b92983..bbae18b2 100755
--- a/test/asm/test.sh
+++ b/test/asm/test.sh
@@ -12,7 +12,7 @@ output="$(mktemp)"
 errput="$(mktemp)"
 rc=0
 
-# Immediate expansion is the desired behaviour.
+# Immediate expansion is the desired behavior.
 # shellcheck disable=SC2064
 trap "rm -f ${o@Q} ${gb@Q} ${input@Q} ${output@Q} ${errput@Q}" EXIT
 
diff --git a/test/fix/test.sh b/test/fix/test.sh
index 0e376d2d..3d89d57b 100755
--- a/test/fix/test.sh
+++ b/test/fix/test.sh
@@ -8,7 +8,7 @@ rc=0
 
 cp ../../{rgbfix,contrib/gbdiff.bash} "$tmpdir"
 cd "$tmpdir" || exit
-# Immediate expansion is the desired behaviour.
+# Immediate expansion is the desired behavior.
 # shellcheck disable=SC2064
 trap "cd; rm -rf ${tmpdir@Q}" EXIT
 
diff --git a/test/link/test.sh b/test/link/test.sh
index 7c51c66d..4abd7268 100755
--- a/test/link/test.sh
+++ b/test/link/test.sh
@@ -9,7 +9,7 @@ gbtemp2="$(mktemp)"
 outtemp="$(mktemp)"
 rc=0
 
-# Immediate expansion is the desired behaviour.
+# Immediate expansion is the desired behavior.
 # shellcheck disable=SC2064
 trap "rm -f ${otemp@Q} ${gbtemp@Q} ${gbtemp2@Q} ${outtemp@Q}" EXIT