I began by giving both the mushrooms a coat of Americana "DuraClear Matte" varnish. When dry, I gave the one on the left a coat of Citadel "Nuln Oil" wash, and the one on the right a coat of thinned Iron Wind Metals "Dark Blue" ink.
When the washes were dry, I drybrushed the one on the left with Reaper MSP Bones "Dungeon Slime". I then painted the underside of the cap, and the tentacles on the righthand one with Crafter's Acrylic "Purple Passion". While the tentacles were still wet, I blended Americana "Cranberry Wine" in on the ends of the tentacles
I realized I couldn't really paint the roots of the mushrooms without painting the bases first, so I took the time at this point to paint the bases on both the mushrooms with Americana "Mississippi Mud". I then painted the bottom of the domed mushroom with Apple Barrel "Apple Lavender", and also used the color to drybrush the top. While that dried, I used some Citadel "Agrax Earthshade" wash to apply a coat to the underside and roots of the conical mushroom. I then went back and used the "Nuln Oil" wash to give a coat to the tentacles, underside, and roots of the domed mushroom.
I let the mushrooms dry overnight and the next day I gave them and their bases a coat of Americana "DuraClear Matte" varnish.