There has been wide debate over recent years as to what the most suitable colour for a fly mask is, however there is no conclusive evidence to suggest that the colour makes any difference to the effectiveness of the fly mask. Many argue that a fly mask with a darker colour mesh is best as it provides a ‘sunglasses’ effect for photosensitive horses, but conversely it can be argued that as dark colours absorb heat a lighter coloured mask is best to reflect radiation instead. These may be points worth considering when purchasing a new fly mask, however there is no scientific evidence to support the significance of either theory.