When I started looking for a mask, I really liked the Grill. The only question was what color? I wanted MultiCam clothing and thought that where I play it's actually more green than tan. Still, the OD/Tan Grill matches up with MultiCam perfectly. My solution was to buy an Olive Grill and paint the eyes tan.
Then, I got a better idea. Just MultiCam the thing. Here's my results with a little bit of a tut on how I did it.
1. First, I taped the entire mask with green 3M automotive tape. Then I gave the mask a coat of Krylon Fusion Camo Khaki. I don't have a picture of this because I didn't intend on making a tut of how to paint your Grill tan. However, when I took the tape off I noticed that there was a tiny bit of overspray on some parts, and some other parts where the paint did not cover all of the black (such as in the crease around the hard plastic). That's when I decided to do a second coat, and then eventually MultiCam.
I learned that the overspray came right off if you scratched it with your fingernail, but wait until the paint has cured to do this otherwise you might chip it where you don't want to. I let my mask cure for 7 days pursuant to the Krylon Fusion instructions.
2. I then re-taped the mask, but not as closely as I had the first time. This time I didn't care about slight overspray because I knew the paint would come off the rubber parts easily. I wanted to make sure to get paint in all the nooks and crannies of the black plastic parts. I first gave it another coat of Camo Khaki, and then added a dusting/stripe of Rustoleum Flat Brown.
Here's another view: (click)
3. Next, I made some female stencils. I searched all over the net for a printable pattern to cut out but I couldn't find anything I liked. So, I just did it freehand with a pencil on some copy paper. When I got some designs I liked, I used a hobby knife to cut them out. Then I taped them on in various places (had to do some trimming as I put them on, in order to conform to the contours of the Grill), and gave a spray-down of Rustoleum Camo Army Green, followed by a gradient of Krylon Fusion Satin Italian Olive.
*additional views:
I finished out this step with a light dusting/gradient of Krylon Fusion Camo Olive:

And stencil removed:
4. Next I made more stencils, much smaller this time, for the highlights and dark spots. I read somewhere (and confirmed by studying the pattern) that these should be grouped in clusters that somewhat form short lines.
And then I taped these on as before, starting with the dark spots. I sprayed them with Rustoleum Camo Earth Brown. After drying time, I took those stencils off and taped on the remaining small stencils.
These got painted first with Valspar Satin Warm Gray, followed by a dusting of Rustoleum Camo Army Green. Then another dusting of Krylon Fusion Camo Khaki. Don't overdo it with the dusting, otherwise you will have to redo this step like I did because the spots will look tan instead of a mix between light green and cream like they're supposed to.
Following all of this, with the stencils removed,

, wait until it's dry and then apply a couple coats of Valspar Flat Clear for protection. If you want, you can also give everything another very light dusting of Krylon Fusion Camo Khaki before clear coating. This is just to tone down the hard lines and green zones; remember, the mask is already mostly olive drab colored, so making the eyes predominantly in the MultiCam brown spectrum works better. But don't overdo it!
Here's the results after the clearcoat:
And here's another shot of my mask with my new Propper ACU's and boonie (Danner Pronghorns in there too):
What do you think? I was skeptical before the clearcoating dried, but after it sat a couple days and really cured, I put it up next to my ACU's and was amazed and how well it really turned out. I love it.