Thanks for responding. Yes, I know for a fact that using the older drivers helps - when I originally installed the card, I used the driver that came on the CD (I don't remember the exact version number, but it was somewhere in the 40's). The color was fine, but the videos wouldn't play - e.g. the LucasArts and Collective logos, the screenshot of the next level which is shown while it is loading, the plane/zeppelin/ship's path shown as a red line on the map in true Indy tradition, etc.
I had been hoping it would be just a setting or two that needed tweaking, but oh well... thanks for your help - I guess I'll dig out my CD and install the older drivers again.