I'm hoping to find something low growing in dark, dark green hue for up front left.
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Looks great! Not a lot of plants get darker green than anubias. Buces certainly do, but they're very expensive right now and, more than likely, poached from the wild in Borneo. Staurogyne repens can be very dark green, but in my experience they lighten up in low tech conditions. Crypts come in some very dark green colors, but I can't think of a foreground appropriate crypt that does so - most of the very small crypts are light green.
I think the best way to achieve the effect of dark green is to contrast the anubias you already have with some light green plants! Pennywort, or maybe a cardamine, would add a nice light green contrast while also adding a leaf/grow pattern type that does not already exist in your tank. I've been having fun recently planting these types of plants behind driftwood and then letting them crawl/spill over it.