An optical device comprising; a colour shifting layer that exhibits different colours dependent on the angle of incidence of incident light, and; an array of substantially transparent microstructures covering at least a part of the colour shifting layer and configured to modify the angle of light incident to, and reflected from, the colour shifting layer, characterized in that said array of microstructures is arranged in accordance with a plurality of pixels of a colour image to be exhibited by the optical device, each pixel exhibiting a uniform colour, wherein; the array of microstructures comprises at least first and second sub-arrays (200a, 200b) of microstructures corresponding to respective first and second colour channels, each sub-array covering an area within a pixel corresponding to the proportion of the respective colour channel within the pixel such that the pixel exhibits the uniform colour, and further wherein; the microstructures of the first sub-array are configured to modify the angle of light incident to, and reflected from, the colour shifting layer in a first manner such that, at a substantially normal viewing angle of the optical device, the first sub array exhibits a base colour and at a first viewing angle of the optical device, the first sub-array exhibits a first colour, wherein said first viewing angle corresponds to viewing the optical device along a direction that is off the normal of the optical device and; the microstructures of the second sub-array are configured to modify the angle of light incident to, and reflected from, the colour shifting layer in a second manner different to the first such that, at a substantially normal viewing angle of the optical device, the second sub-array exhibits said base colour and at said first viewing angle, the second sub-array exhibits a second colour different from the first colour; such that at a substantially normal viewing angle, the optical device exhibits the base colour, and at said first viewing angle, the optical device exhibits the colour image. a colour shifting layer that exhibits different colours dependent on the angle of incidence of incident light, and; an array of substantially transparent microstructures covering at least a part of the colour shifting layer and configured to modify the angle of light incident to, and reflected from, the colour shifting layer, characterized in that said array of microstructures is arranged in accordance with a plurality of pixels of a colour image to be exhibited by the optical device, each pixel exhibiting a uniform colour, wherein; the array of microstructures comprises at least first and second sub-arrays (200a, 200b) of microstructures corresponding to respective first and second colour channels, each sub-array covering an area within a pixel corresponding to the proportion of the respective colour channel within the pixel such that the pixel exhibits the uniform colour, and further wherein; the microstructures of the first sub-array are configured to modify the angle of light incident to, and reflected from, the colour shifting layer in a first manner such that, at a substantially normal viewing angle of the optical device, the first sub array exhibits a base colour and at a first viewing angle of the optical device, the first sub-array exhibits a first colour, wherein said first viewing angle corresponds to viewing the optical device along a direction that is off the normal of the optical device and; the microstructures of the second sub-array are configured to modify the angle of light incident to, and reflected from, the colour shifting layer in a second manner different to the first such that, at a substantially normal viewing angle of the optical device, the second sub-array exhibits said base colour and at said first viewing angle, the second sub-array exhibits a second colour different from the first colour; such that at a substantially normal viewing angle, the optical device exhibits the base colour, and at said first viewing angle, the optical device exhibits the colour image.