Here's how one Hometalker coloured theirs
cut it off place grass to desired length place top of grass in lrg tub with food coloring in water alot for more colorful grass and let it sit how ever long to get color you want barely dipping for more pastel colors. remove gently from water/dye solution hang each piece upside down to dry thoroughly. Place in container/basket/vase or hang in bundles; to keep grasses from falling apart or further seeding you can lightly spray them with extra hold hairspray Aqua Net Super hold works well here's video on dyeing grasses https://www.youtube.com/watch?v=tpZbzOxLa5w
Hi Liz, cut the grass before it starts to grow back for the season, pick the area you want to cut and dye, then use some duct tape as close to the ground as you can and bind it together with the tape. once it's bound with the tape cut it off and the tape will hold it together for you to dye it., you could use florist wire as well and leave it on to hold it together after dying.
Put some food colouring in some water in a spray bottle. Put the nozzle on fine mist and spray until all the pampus grass is covered.