Ok, Let's...

I've used the same ballast recently.  Here's what it looks like on the layout, before this scene was completed:

This seems close to some of your prototype ballast.

In the above location, the Scenic Express "blended" is on the center track.  Scenic Express "dark gray" is on the mainline at right, while the secondary tracks at left have mixtures of two different colors of sand, with some of the Scenic Express blended here and there.

I wouldn't hesitate to mix several different colors to get the right look.

What about Grout?

I remember from one of Mike Confalone's how-to videos that he used un-sanded colored grout to change the color of some loose rip-rap rocks.  I wonder if I could do the same here.  Anyone know how grout would react to alcohol and water when laying the ballast down?

a possible idea

On a previous layout I used Joe Fugate's technique of the zip-texturing(plaster mixed with powder paint or I use grout tint). I used this and I still do use this techique like I said for many things. The zip-texturing powder hardens when you spray it with water. So, maybe if you blend a mix of your ballast and a mix of plaster or hydrocal with some grey grout tint or just plain plaster maybe you could thin down the color to a lighter grey. If you do this I wouldn't add a whole lot of this powder to the ballast for many reasons. This technique could probably just make the ballast a shade lighter. Just a thought.

About the similarity of our layouts. As I posted on another blog, you were on of the first people just by your blog and videos to actually incourage me to model that region. I'm a big BN buff and started this layout I was looking for a prototypical branch line of the BN in Washington state. I just happened to stumble on one of your videos and I started researching that area a little more and happened to stumble on the Kettle Falls to Nelson line. I live in San Diego so, it's hard to do research on it but, it's a great place to model nevertheless. I really enjoy your vids. and your blog.