I found the Petty Blue paint!

VIA Wikipedia...One of the most distinctive features of the No. 43 car is its color. Petty Blue, as it's called, was created by the Petty family. According to Richard, the color was created by accident when they didn't have enough white or dark blue paint to cover the entire car. The resulting mix of white and blue proved to be very popular and remains on the No. 43 car to this day.[5] Rumors state that Richard Petty would not allow STP to sponsor his car unless he could keep it painted blue. A compromise was reached to paint the car half Petty Blue and half STP Red. Thus was born one of the most famous paint schemes in racing history.