Those are two strands of Harris Tweed from two ends of the same skein. Not a ball, cut and spliced to the necessary weight. That’s the same skein. I know one should expect natural variations from a natural fibre like wool, but come on. It’s stripey!
That being said, I’m not too sad about it. I made the discovery a point when I could use it so it looks like a ‘design element’ rather than a cock-up (no, I didn’t ball up all the yarn before I started knitting, that’s just not my way). I’ve divided the stripey bit in half and am using it for the lower half of the sleeves of my back-laced tunic. I think I can get away with it. This isn’t massively different, right?