Just an FYI - not all Rocky Mtn dirt is the same color/shade - in my area it varies from red to a gray/brown.
That being said, there are some things that you might consider-
Lighting:
Look to the color of your lighting - if it doesn’t closely match sunlight, that could be what’s throwing your color off. Lighting that has a rating of about 5500-6000 Kelvin, probably comes the closest to matching sunlight on a cloudless day at noon.
Light intensity - another thing that can throw color off, although not as much as the color. Higher intensity lighting can make color appear lighter in tone, and why the dirt appears lighter outside than inside.
Type of lighting - depending on your specific light source, it can be enhancing some colors and muting other colors.
Age of your bulbs - with the exception of incandescent lighting as bulbs age, the spectrum that they emit, also changes - this is why folks that have reef aquariums ( which require a controlled spectrum of light to ensure the health of corals while minimizing out breaks of algae ) change bulbs every 6-12 months, because as HM and Fluorescent bulbs age, the spectrum of light tends to shift towards the red end of the spectrum.
Small differences of more than one issue can add up to cause a bigger change in appearance than any one of them alone.
That being said, there are some things that might work to change the appearance of the dirt, without changing your lighting or the actual dirt being used.
Subtly darken everything else - this will make the dirt appear lighter. This will also cause lighter colors ( like gras
My wife bought a thing of tube sand for a different project. It looked interesting, so I sifted a little of it. Looks like it will work for dirt roads just fine. Sort of fits the color you describe. Just a thought.
One thing whenever using real dirt is to be sure you run a strong magnet over it before putting it on your layout. This will get rid of any metal fragments in the dirt that could get into your locos and mess up the motors.
Forgot to say, check to see if your local hardware store has a damaged bag of tube sand. Not only could you see what the color was, but it would reduce the price.
Just had a thought - Hobby Lobby ( or other craft store ) often have different shades of colored sand for sand painting and similar projects, and it’s usually fairly fine.
Between all the various Woodland Scenics colors one should be able to blend up any color that is needed.
Using real sand can become heavy. This might not be an issue with your layout. I had a modular unit that I purposely made light weight (foam construction). As I picked up the coffee can of sand I was going to use I realized the can was heavier than the entire module. Needless to say, I did not use real sand but went and purchased the WS materials (as above).
After reading this thread I started going through my billions of rocky mountain pics. I spend a lot of time up there. The one thing I noticed. Everything that is not a sharp granite cliff is covered in vegetation. Light plays a huge roll in colour. Find a pile of dirt in your back yard and take a picture of it over a number of days, and at different times of the day, and in different weather conditions. It can look very different each time.
Look at the difference in colour on this mountain just from the shade of the cloud.
Different shades again caused by being in the trees. This is the remains an old snow shed from the 1880s. It is on the original CPR line through the Rockies.
Here I have sent the kids on ahead to check for Grizzly Bears. In the Rockies ( at least in Canada ) it’s Granite or the always encroaching jungle. You don’t see much dirt.
Most of my narrow gauge buddies who model Colorado and myself (not narrow gauge) use real dirt from around our area (Bay Area CA). I have been able to find some light tan in various places nearby, You can probably find something close in your area. look in road cuts, riverbanks etc for the real stuff.
I have used plaster and powdered pigments to lighten the color of some of my dirt to an acceptable tint. I agree with the earlier advice about getting your lighting as you want it before you set about adjusting the tint.
You might try tinted tile grout if you cant find anything close…much cheaper than buying a commercial modeling product.
Have you looked at the colored grout in a building supply store. Lots of colors and comes with its own adhesive, just add water and go.
I have used this on my layout. Lay a base of white glue on the area to be sceniced, sread the grout and finish with a mist of water. The grout does dry a shade darker than you would see on the box so buy it one shade lighter.
