After shooting to death an unarmed store manager in a holdup at a McDonald's restaurant in Northeast Washington last March, two men emptied the store's safe and cash registers and fled carrying bags of money. Yesterday, the men were found guilty of murder in D.C. Superior Court--convicted largely because of hidden devices that dyed the money red.

Within moments after the men had run out of the McDonald's on Nannie Helen Burroughs Avenue last March 16, tiny devices in the cash detonated, spreading a red dye and tear gas that stained the money and the men's clothes.

Stains left on clothing and a .38-caliber revolver provided police with a trail that eventually led to D.C. Superior Court, where a jury yesterday found David M. Jones, 30, and John R. Young, 33, guilty of first-degree murder in the slaying of manager George Knights.

In addition, each man was convicted of four counts of armed robbery, two counts of assault with a dangerous weapon and a single charge of carrying a pistol without a license.

Jones and Young each face maximum sentences of life in prison. Chief Judge H. Carl Moultrie I set sentencing for March 4.

Prosecutors said the case was the first time the red dye, used by many banks to foil robberies, has provided the crucial evidence in a murder trial. McDonald's officials said the verdict is the first time a robbery of one of their outlets has been closed with the use of the dye device, which they said is being considered for widespread use in the chain's 7,000 franchises.

McDonald's officials had decided to increase security at the Nannie Helen Burroughs store with the red dye devices after a security guard was killed, two months before the March 16 incident, when a robber shot him in the face with a shotgun.

Employes testified that Young, also known as John R. Young-Bey, stood at the front counter and ordered cashiers to empty their cash drawers. Jones, meanwhile, vaulted the counter and went to the back of store, where he demanded that Knights open the safe.

Both men carried pistols, according to testimony at the trial. For reasons unknown, Jones shot Knights in the back of the head at point-blank range, then stuffed cash from the safe into a plastic shopping bag.

The red dye devices were triggered when the men left the store. Police later found Jones' shopping bag where he had dropped it about 200 yards away. Young escaped clutching a paper bag full of stained cash.

Jones, an escapee from Lorton Reformatory, was arrested three days later at an apartment on Hillside Road SE by police responding to an anonymous tip. Police were led to Young on March 22 when he attempted to spend some pink bills at a nearby supermarket.

A woman who lived at the apartment where Jones was arrested testified at the trial that Jones tried cleaning the stolen money with various household cleansers, even scrubbing them with nail polish remover and a toothbrush in the kitchen sink.

When police arrived to arrest him, Jones answered the door holding a .38-caliber revolver stained with dye. Police seized a blue parka and several other articles of Young's clothing that also were stained.

At the trial, an FBI chemist testified that stains on the gun and clothing were made by a rare dye that has only two uses: military flares and security devices such as the ones used at the McDonald's store.