Varnish roan, to the extent of my knowledge, is the type of roaning that Appys normally get. They have a lot more white covering up the color, hence the name "varnish", like when you put a clear coat of varnish over paint to seal it. (It looks white at first.) :)
Yup, varnish roan, and many (not all) varnish roans will get whiter year after year. My first horse stormy was a blue varnish roan - he is still kicking now in his 30's but appears white other than like 3 spots on his rump.