The all black micarta you are seeing is micarta that was made from the start black. Micarta can be made in just about any color. Micarta is made with several layers of canvas, linens, burlap even paper and any thin material. Use red canvas you get red micarta. It's a process of several layers with resins. I think like Jonny1280 said the hard resin doesn't allow the dye or stain to penetrate . The only reason I think your able to darken the micarta is the fuzzy texture left from the sanding with something very rough. If you were to sand your scales with fine sandpaper you would end up with very smooth scales and I don't think you would be able to change the color unless you use paint. You can always change the texture to your likes of any scale material by sanding and using different grits. Hope this helps.
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The middle is black and white canvas the the top and bottom all black the bottom has been sanded with med.grit emery cloth. Just want to say I do like the color of your scales a lot