Coloring sawdust "grass" - update

I asked the group about coloring Lionel type sawdust grass with Rit dye about a year ago, and received comments that the dye would fade rapidly from UV and to use thinned acrylic paint instead. I took that advice and completed the simulated 1920's Lionel layout for display in the city museum's old toy store. The layout had been in the south east facing front window of the store for about 9 months. We just removed it for a train show, and I am happy to report that the sawdust looks just as good as when prepared last year. Unfortunately, I can't say the same for a black posterboard highway (now a medium brownish gray) and for the Life-like scenery paper (whose green is now turquoise blue) used to simulate the original Lionel mottled craft paper ground covering. Again, thanks to the newsgroup for your good advice. Gary Q