diff --git a/agb/src/display/tiled/vram_manager.rs b/agb/src/display/tiled/vram_manager.rs
index 2a482a69..4339d56b 100644
--- a/agb/src/display/tiled/vram_manager.rs
+++ b/agb/src/display/tiled/vram_manager.rs
@@ -463,9 +463,16 @@ impl VRamManager {
     }
 
     /// Gets the index of the colour for a given background palette, or None if it doesn't exist
-    pub fn find_colour_index_16(&mut self, palette_index: usize, colour: u16) -> Option<usize> {
+    #[must_use]
+    pub fn find_colour_index_16(&self, palette_index: usize, colour: u16) -> Option<usize> {
         assert!(palette_index < 16);
 
         (0..16).find(|i| PALETTE_BACKGROUND.get(palette_index * 16 + i) == colour)
     }
+
+    /// Gets the index of the colour in the entire background palette, or None if it doesn't exist
+    #[must_use]
+    pub fn find_colour_index_256(&self, colour: u16) -> Option<usize> {
+        (0..256).find(|&i| PALETTE_BACKGROUND.get(i) == colour)
+    }
 }