Currently, there is a distinct color difference between the two formulations.
Chevron Supreme 5W-30, from a bottle dated May 06, is a golden/yellow color and relatively clear.
The Havoline 5W-30 that I observed from a 5qt jug, during the same time frame, had a darker reddish-brown color and was somewhat cloudy.
While the published product data sheets are very close for Havoline & Supreme, the color is a tip-off that different brands of addivives are being used and the product coming off the bottling lines is indeed different.