Deep Blue is a fanmade Sing-a-ma-jig. He is deep blue, has dark purple hair, the same ears as the big one from the Purple duet, black circle eyes, a red nose, a lime green mouth, the same arm pose as the new red one, a green shirt with blue-green stripes, the same feet as the red Sing-a-ma-jig and the same voice as the Skeleton. He sings "Teddy Bear's Picnic". He counts to 15. Most ffanmade sing a ma jigs count to 10.
Here's how he signs on, enters song and counting mode and signs off:
Sign on: Hey there.
Song mode entry: Sing it.
Counting mode: Let's count to 15!
Sign off: Later man.
This is what he looks like.