diff --git a/agb-image-converter/src/colour.rs b/agb-image-converter/src/colour.rs
index 917b3b99..b401b9bd 100644
--- a/agb-image-converter/src/colour.rs
+++ b/agb-image-converter/src/colour.rs
@@ -1,3 +1,5 @@
+use std::str::FromStr;
+
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
 pub struct Colour {
     pub r: u8,
@@ -20,3 +22,22 @@ impl Colour {
         self.a != 255
     }
 }
+
+impl FromStr for Colour {
+    type Err = String;
+
+    fn from_str(colour: &str) -> Result<Self, Self::Err> {
+        if colour.len() != 6 {
+            return Err(format!(
+                "Expected colour to be 6 characters, got {}",
+                colour
+            ));
+        }
+
+        let r = u8::from_str_radix(&colour[0..2], 16).unwrap();
+        let g = u8::from_str_radix(&colour[2..4], 16).unwrap();
+        let b = u8::from_str_radix(&colour[4..6], 16).unwrap();
+
+        Ok(Colour::from_rgb(r, g, b, 255))
+    }
+}
diff --git a/agb-image-converter/src/config.rs b/agb-image-converter/src/config.rs
index eaa2cd20..075a9f7d 100644
--- a/agb-image-converter/src/config.rs
+++ b/agb-image-converter/src/config.rs
@@ -23,6 +23,7 @@ pub(crate) fn parse(filename: &str) -> Box<dyn Config> {
 pub(crate) trait Config {
     fn crate_prefix(&self) -> String;
     fn images(&self) -> HashMap<String, &dyn Image>;
+    fn transparent_colour(&self) -> Option<Colour>;
 }
 
 pub(crate) trait Image {
@@ -36,6 +37,7 @@ pub(crate) trait Image {
 pub struct ConfigV1 {
     version: String,
     crate_prefix: Option<String>,
+    transparent_colour: Option<String>,
 
     image: HashMap<String, ImageV1>,
 }
@@ -53,6 +55,21 @@ impl Config for ConfigV1 {
             .map(|(filename, image)| (filename.clone(), image as &dyn Image))
             .collect()
     }
+
+    fn transparent_colour(&self) -> Option<Colour> {
+        if let Some(colour) = &self
+            .transparent_colour
+            .as_ref()
+            .map(|colour| colour.parse().unwrap())
+        {
+            return Some(*colour);
+        }
+
+        self.images()
+            .values()
+            .flat_map(|image| image.transparent_colour())
+            .next()
+    }
 }
 
 #[derive(Deserialize)]
@@ -69,19 +86,9 @@ impl Image for ImageV1 {
     }
 
     fn transparent_colour(&self) -> Option<Colour> {
-        if let Some(colour) = &self.transparent_colour {
-            if colour.len() != 6 {
-                panic!("Expected colour to be 6 characters, got {}", colour);
-            }
-
-            let r = u8::from_str_radix(&colour[0..2], 16).unwrap();
-            let g = u8::from_str_radix(&colour[2..4], 16).unwrap();
-            let b = u8::from_str_radix(&colour[4..6], 16).unwrap();
-
-            return Some(Colour::from_rgb(r, g, b, 255));
-        }
-
-        None
+        self.transparent_colour
+            .as_ref()
+            .map(|colour| colour.parse().unwrap())
     }
 
     fn tilesize(&self) -> TileSize {
diff --git a/agb-image-converter/src/palette16.rs b/agb-image-converter/src/palette16.rs
index afb50c68..2878bad6 100644
--- a/agb-image-converter/src/palette16.rs
+++ b/agb-image-converter/src/palette16.rs
@@ -58,7 +58,7 @@ impl Palette16 {
             }) as u8
     }
 
-    pub fn colours<'a>(&'a self) -> impl Iterator<Item = &Colour> + 'a {
+    pub fn colours(&self) -> impl Iterator<Item = &Colour> {
         self.colours.iter()
     }
 
@@ -167,7 +167,10 @@ impl Palette16Optimiser {
     fn find_maximal_palette_for(&self, unsatisfied_palettes: &HashSet<Palette16>) -> Palette16 {
         let mut palette = Palette16::new();
 
-        palette.add_colour(self.transparent_colour.unwrap_or_else(|| Colour::from_rgb(255, 0, 255, 0)));
+        palette.add_colour(
+            self.transparent_colour
+                .unwrap_or_else(|| Colour::from_rgb(255, 0, 255, 0)),
+        );
 
         loop {
             let mut colour_usage = vec![0; MAX_COLOURS];