diff --git a/src/main/java/dan200/computercraft/core/terminal/Terminal.java b/src/main/java/dan200/computercraft/core/terminal/Terminal.java
index f6e647bb3..91d6ffe2b 100644
--- a/src/main/java/dan200/computercraft/core/terminal/Terminal.java
+++ b/src/main/java/dan200/computercraft/core/terminal/Terminal.java
@@ -419,6 +419,7 @@ public class Terminal
     {
         if( c >= '0' && c <= '9' ) return c - '0';
         if( c >= 'a' && c <= 'f' ) return c - 'a' + 10;
+        if( c >= 'A' && c <= 'F' ) return c - 'A' + 10;
         return 15 - def.ordinal();
     }
 }
diff --git a/src/main/resources/data/computercraft/lua/rom/apis/window.lua b/src/main/resources/data/computercraft/lua/rom/apis/window.lua
index feafa00c2..724cda155 100644
--- a/src/main/resources/data/computercraft/lua/rom/apis/window.lua
+++ b/src/main/resources/data/computercraft/lua/rom/apis/window.lua
@@ -265,6 +265,8 @@ function create(parent, nX, nY, nWidth, nHeight, bStartVisible)
         if #sTextColor ~= #sText or #sBackgroundColor ~= #sText then
             error("Arguments must be the same length", 2)
         end
+        sTextColor = sTextColor:lower()
+        sBackgroundColor = sBackgroundColor:lower()
         internalBlit(sText, sTextColor, sBackgroundColor)
     end