the color change is normal- my rhubarb wine is a light golden color, not red at all.
You added a ton of extra acid, and rhubarb is pretty acidic already, so it's possible that the flavor is just acidic and young.
I'd rack it when lees are 1/4 inch think, keep it topped up to within an inch of the bung, and place it in a dark place for 6 months or so. It should improve/
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