It's very hard to say, as Midleton don't like to divulge how much of anything they put into their whiskeys. However, it's made from a pot still whiskey made from a mash of malted and unmalted barley, probably in the ratio of about 45:55. It is then blended with grain whiskey, but I don't know the proportion of grain in the mix.
The one good thing I can say is that it is not coloured. But as Aidan says Midelton do not divulge that type of info unfortunately.
However in general quality irish blends have a high % of potstill or malt in comparison to Scotch blends. For example a 20% blend of potstill or malt(picking a number out of the air) would be considered a high % of the total blend. Blackbush has circa 70% malt in the blend which is unheard of in scotch blends