Spruce Green is the blue-green color, dyed first with indigo, then over-dyed with apple bark or turmeric or weld. Each of these yellows vary in availability and strength, so I use what seems best based on the strength of the indigo that day.
I switched over from black beans to indigo in the late summer of 2017 and have been slowly converting ALL my blues and greens. Indigo is light-fast and washes well. I treat it with two finishing steps after dyeing. First I soak it in a vinegar-water bath to balance the PH, a standard process. Next I soak the yarn in Eucalan to soften and condition the yarn.