The Yellow Mercury Marquee was very distinctive, its color really stood out especially when I saw it shown on TV still parked along I-35. You would remember seeing this color of car on the highway when it was pulled over by a Highway patrol trooper with flashing lights and another vehicle that pulled over with it.
The witnesses at Travelers Aid also saw the car on April 18, 1995 in OKC in front of their building and it was distinctive to them and they vividly remembered the car just as the librarian. Both of these are real stories and the witnesses are very credible.
It was a Mercury Marquis not a Mercury Marquee. Sorry for propagating the spelling error.