Royal Blue is a fanmade Sing-a-ma-jig with the "Voice Wiggle Effect". He has the same shape of ears as the snowman Sing-a-ma-jig, has black circle eyes, a yellow nose, a pink mouth just like the big one from the royal blue duet, wears a black and white striped shirt, the same arm pose as the Mint Green Sing-a-ma-jig, the same shape of feet as the light blue Sing-a-ma-jig, the same voice as the red "All Star" Sing-a-ma-jig and he sings "High Hopes". He signs on by saying "Hi There!", enters song mode by saying "Sing With Me!" and signs off by saying "See You Soon!". He looks a whole lot like the big one from the royal blue duet.
Royal blue sing a ma jig

This is what he looks like.