"Hi-ho, boys and girls! It's time to change the change."

Those words--or something pretty much like them--soon will start flowing from the government's newest spokesman, or as the U.S. Mint put it, "spokesfrog."

The Treasury Department agency announced yesterday that it had hired Kermit the Frog, one of the Muppet creations of the late Jim Henson, to help promote its new series of 50 state commemorative quarters. The Mint said it had signed a three-year contract with the Jim Henson Co. that will allow it to use Kermit in an "extensive print and broadcast campaign to educate Americans of all ages on America's newest change."

The first of the new quarters, for Delaware, Pennsylvania and New Jersey, have been released and the series is scheduled to run for 10 years. Mint officials are expecting to make millions of dollars on the coins, which will be sold in special silver and uncirculated sets.

Mint Director Philip N. Diehl welcomed Kermit as "one of America's great storytellers," who would help the Mint use the coins to tell the story of the 50 states.

How much the Mint will have to pay for its green spokesman is still being negotiated, Diehl said.

If the Treasury would only agree to change the greenback, as some members of Congress are urging, Kermit would be a natural to promote a new dollar bill. But, then, as Kermit often has said: "It's not easy being green."

CAPTION: U.S. Mint Director Philip N. Diehl with Kermit the Frog, spokesman for coin series commemorating U.S. states.