We just planted a 6-7' tall Japanese Emperor I this weekend. I'm curious to see what the spring, summer, fall leaf colors look like.
I've heard they can be from blood red to almost a purple.
'Emperor I' is very close to 'Bloodgood' in appearance and will take on very similar seasonal color changes. Bright red new spring growth, followed by deeper burgundy full season color and scarlet/orange in fall. Exact coloring can be influenced by soil conditions, siting and the characteristics of the clone providing the graft stock but it will be pretty similar to that described above.
Try Googling under either of those cultivar names for seasonal images for additional clarification.