It unveiled their Jubilee bus at its Hastings depot with managing director Joel Mitchell and Lord Brett McLean from Hastings.
The livery, made up of royal purple and reflective silver paint, has a distinctive look.
Anne Menzel marketing manager for Stagecoach South East who created the regal design, said: “Should the bus be spotted at night with light shining on it, the silver reflects.”
The bus company says it has gone all out to celebrate with two buses wrapped in the livery.
Stagecoach staff have also been filling their depots with balloons, paper crowns and bunting in preparation for the double bank holiday.
Managing director Joel Mitchell said: “It's so exciting to have these buses out on the roads as Jubilee fever kicks in.
“We’re witnessing this once in a lifetime event and we all feel incredibly lucky to play a part in these celebrations.”