Don't think you can, easily...all cars of that era used clear bulbs in the cluster, with filters under the gauges for whatever colors they were using (green on these ones). Only real option is to buy an indiglo gauge cover kit.
It's possible to take apart the gauge cluster and scrape the green film away. Should produce a yellow/white light. Then swap the bulbs for colored ones, red blue pink. so on.
There aren't many ways other than what Red LX said as the easier option or reverse glow.