Seems to me this is the opposite of a Fiberon Decking fail. They replaced all of the miscolored decking even after you had cut and installed it. I think that shows they stand not only behind their products but behind their brand and their reputation. This was a customer service WIN and it's so refreshing to see a company taking responsibility for client satisfaction in such a huge way. Kudos to you, Fiberon!
Always assume products are from different batches. It shouldn't be a big deal, but before you start cutting, MIX THEM UP. Especially after you noticed the issue. Every tile guy has this happen on a job. It's normal. You just need to alternate what stack you source from.
I can understand you wanted to finish the project. But why would you continue knowing you have two different lots or finishes? I would have stopped as soon as I noticed the issue, if not before starting to lay it down. You could have returned the material without cutting it and if nothing else, gone with another brand.
Just had a Fiberon Promenade deck installed 2 weeks ago and I have something similar going on. waiting for the local Fiberon Rep to contact me to come out and take a look. Hope they pay for both the decking and cost to replace.
I wouldn't ever use those post base brackets I'd spend the extra couple bucks for the bracket with the metal spacer below the post so the post isn't sitting on the ground, it'll rott away sooner than you think