Refering to page 116 in Dr. Brown's book:
King of Siam has cream to light pink spots on a green field; Wizard of Oz is another name for King of Siam that may have some more pink in it; I maintain the pink is a function of leaf age and light conditions and the natural variation in the cultivar. It is a vigorous grower.
Queen of Siam has a lot of reds in it - red and reddish orange dots on a green field; nothing subtle about this cultivar. It is also much slower and less cold resistant that King of Siam which has never defoliated for me and has adapted to anything from shade up to full sun.