diff --git a/colour-space.cabal b/colour-space.cabal
--- a/colour-space.cabal
+++ b/colour-space.cabal
@@ -2,7 +2,7 @@
 -- documentation, see http://haskell.org/cabal/users-guide/
 
 name:                colour-space
-version:             0.1.5.0
+version:             0.1.5.1
 synopsis:            Instances of the manifold-classes for colour types
 -- description:         
 homepage:            https://github.com/leftaroundabout/colour-space
diff --git a/src/Data/Colour/Manifold.hs b/src/Data/Colour/Manifold.hs
--- a/src/Data/Colour/Manifold.hs
+++ b/src/Data/Colour/Manifold.hs
@@ -92,6 +92,8 @@
   fromFlatTensor = LinearFunction $ \(Tensor (RGB r g b)) -> ColourNeedle (RGB r g b)
   addTensors (Tensor (RGB r g b)) (Tensor (RGB r' g' b'))
                 = Tensor $ RGB (r^+^r') (g^+^g') (b^+^b')
+  subtractTensors (Tensor (RGB r g b)) (Tensor (RGB r' g' b'))
+                = Tensor $ RGB (r^-^r') (g^-^g') (b^-^b')
   negateTensor = LinearFunction $ \(Tensor (RGB r g b))
                        -> Tensor (RGB (negateV r) (negateV g) (negateV b))
   scaleTensor = bilinearFunction $ \μ (Tensor (RGB r g b))