Try bleeding the master cylinder at the line fitting. If the fluid is dark, then it is the master that is causing the dark fluid color. It could also be both cylinders. If it's been a while (or never) since either has been replaced or rebuilt, then replace them.
PANTERA INTERNATIONAL
A DE TOMASO CAR CLUB
Presents the De Tomaso Forums
The On-Line Meeting Place for De Tomaso Owners and Enthusiasts From Around the World
Clicking on the banner will take you to the sponsor's website.