You're not going to to be able to stain those dark shakes a light color, or "wash off the old color." You could paint them, but that will take a lot of prep and priming, and cedar shakes are notorious for bleeding through paint and for causing rusting around any exposed fasteners which will also show through the paint. I think you have the following choices:

1. Learn to love the traditional look you have

2. Paint them, spending a lot of time on prep, and hope that you don't end up with appearance problems later

3. Remove them and start over

Mmmmm...if painting or washing the shingles is pretty much a non-starter per kudzu, maybe consider painting your trim a deep rich green or charcoal? And then paint your front door some fashionable contrasting (lacquer) color. Lots of new houses are going up with dark siding and trim around here and the dark trim is classic, i.e., in Nantucket or Bar Harbor.. Just an idea, and I know not the look you’re after but might be an option. Good luck.

I like it
We’re going to try and clean up the existing shake and once we do, we will look at options for trim.

I have worked with this problem in the past. I have found that once the shakes have darken to that point they really don’t get much lighter with cleaning. Some but not a lot. I would however look into opaque stains. There are many Medium to medium dark colors that would look beautiful on your house and will cover the darkness nicely.