diff --git a/TODO.md b/TODO.md
index 0c6c007..b0e7f36 100644
--- a/TODO.md
+++ b/TODO.md
@@ -14,6 +14,7 @@
  - Tuple operations
  - we don't need vectors as arguments to operators
  - Assignment tests
+ - Color check is too slow
 
 ## Parser
  - Better error when `sin = 2`