diff --git a/catppuccin/colour.py b/catppuccin/colour.py
index 820c90e..193eea7 100644
--- a/catppuccin/colour.py
+++ b/catppuccin/colour.py
@@ -15,29 +15,48 @@ class Colour:
     red: int
     green: int
     blue: int
+    alpha: int = 255
 
     @property
     def rgb(self) -> Tuple[int, int, int]:
         """Get the colour as a 3-tuple of red, green, and blue."""
         return self.red, self.green, self.blue
 
+    @property
+    def rgba(self) -> Tuple[int, int, int, int]:
+        """Get the colour as a 4-tuple of red, green, blue, and alpha."""
+        return self.red, self.green, self.blue, self.alpha
+
     @property
     def hex(self) -> str:
         """Get the colour as a lowercase hex string."""
+        if self.alpha < 255:
+            return f"{self.red:02x}{self.green:02x}{self.blue:02x}{self.alpha:02x}"
         return f"{self.red:02x}{self.green:02x}{self.blue:02x}"
 
     def __eq__(self, other: Any) -> bool:
         if not isinstance(other, Colour):
             raise ValueError("Cannot check equality with non-colour types.")
+
         return self.hex == other.hex
 
     @classmethod
     def from_hex(cls, hex_string: str) -> Colour:
-        """Create a color from hex string."""
-        if len(hex_string) != 6:
-            raise ValueError("Hex string must be 6 characters long.")
-        match = re.match(r"([\da-fA-F]{2})" * 3, hex_string)
+        """Create a colour from hex string."""
+        if len(hex_string) not in (6, 8):
+            raise ValueError("Hex string must be 6 or 8 characters long.")
+
+        num_groups = 3 if len(hex_string) == 6 else 4
+        match = re.match(r"([\da-fA-F]{2})" * num_groups, hex_string)
         if match is None:
-            raise ValueError("Hex string have an invalid format.")
-        hex_r, hex_g, hex_b = match.groups()
-        return Colour(*(int(col, 16) for col in (hex_r, hex_g, hex_b)))
+            raise ValueError("Hex string has an invalid format.")
+
+        components = (int(col, 16) for col in match.groups())
+        return Colour(*components)
+
+    def opacity(self, opacity: float) -> Colour:
+        """Return a new colour with the given opacity."""
+        if not 0 <= opacity <= 1:
+            raise ValueError("Opacity must be between 0 and 1.")
+
+        return Colour(self.red, self.green, self.blue, int(opacity * 255))
diff --git a/tests/test_colour.py b/tests/test_colour.py
index 4c4ab61..3c47806 100644
--- a/tests/test_colour.py
+++ b/tests/test_colour.py
@@ -7,14 +7,30 @@ def test_colour_to_rgb():
     assert Colour(12, 123, 234).rgb == (12, 123, 234)
 
 
-def test_colour_to_hex():
+def test_colour_to_rgba():
+    assert Colour(12, 123, 234, 35).rgba == (12, 123, 234, 35)
+
+
+def test_colour_to_rgba_default():
+    assert Colour(12, 123, 234).rgba == (12, 123, 234, 255)
+
+
+def test_rgb_colour_to_hex():
     assert Colour(0x12, 0xEB, 0x77).hex == "12eb77"
 
 
-def test_hex_to_color():
+def test_rgba_colour_to_hex():
+    assert Colour(0x12, 0xEB, 0x77, 0x35).hex == "12eb7735"
+
+
+def test_hex_to_colour():
     assert Colour.from_hex("12eb77") == Colour(0x12, 0xEB, 0x77)
 
 
+def test_hex_to_colour_with_alpha():
+    assert Colour.from_hex("12eb7735") == Colour(0x12, 0xEB, 0x77, 0x35)
+
+
 def test_invalid_hex():
     for invalid_value in ("1234567", "12345", "Z00000", "ABCDEG", "0F7CBJ"):
         with pytest.raises(ValueError):
@@ -27,3 +43,13 @@ def test_equality():
 
     with pytest.raises(ValueError):
         assert Colour(0x12, 0xEB, 0x77) == 42
+
+
+def test_opacity():
+    colour = Colour(0x12, 0xEB, 0x77).opacity(0.5)
+    assert colour == Colour(0x12, 0xEB, 0x77, 0x7F)
+
+
+def test_opacity_invalid():
+    with pytest.raises(ValueError):
+        Colour(0x12, 0xEB, 0x77).opacity(1.5)