Different clusters form different values

I have 3 images and have clustered into 3 clusters,

for example i have clustered blue colour into one cluster ,wen i took mean of it ,all 3 images of that blue colour which are clustered are different,plz tell why i get different mean for same colour

my images

http://www.sendspace.com/file/zlh77t

http://www.sendspace.com/file/96u93a