Honor the NO_COLOR environment variable.

src/compare/diff.rs

@@ -131,26 +131,42 @@ impl DiffResult {
     }
 
     fn foreground_color(red: u8, green: u8, blue: u8) -> String {
-        format!(
-            "\x1b[38;2;{red};{green};{blue}m",
-            red = red,
-            green = green,
-            blue = blue
-        )
+        if DiffResult::should_use_color() {
+            format!(
+                "\x1b[38;2;{red};{green};{blue}m",
+                red = red,
+                green = green,
+                blue = blue
+            )
+        } else {
+            String::new()
+        }
     }
 
     #[allow(dead_code)]
     fn background_color(red: u8, green: u8, blue: u8) -> String {
-        format!(
-            "\x1b[48;2;{red};{green};{blue}m",
-            red = red,
-            green = green,
-            blue = blue
-        )
+        if DiffResult::should_use_color() {
+            format!(
+                "\x1b[48;2;{red};{green};{blue}m",
+                red = red,
+                green = green,
+                blue = blue
+            )
+        } else {
+            String::new()
+        }
     }
 
     fn reset_color() -> &'static str {
-        "\x1b[0m"
+        if DiffResult::should_use_color() {
+            "\x1b[0m"
+        } else {
+            ""
+        }
+    }
+
+    fn should_use_color() -> bool {
+        !std::env::var("NO_COLOR").is_ok_and(|val| !val.is_empty())
     }
 }