Siding darkening over time

I realize this is more of a deck web site but thought the information would be applicable to wood siding also. I have Cedar / Redwood siding and used the typical Behr or Cabot wood cleaners/ brighteners to get the wood back to a light red color. I then used Penofin Red label Redwood color and at first the siding had a fairly light red color to it. After 3-4 years it has turned more of an ugly dark brown. Now I have to pressure wash the whole house and brightening up again before staining. If I had known of your review that Penofin Blue label would not darken like the Red label it could have saved me a lot of work. The most important item for me is will the color stay the same as when I put it on. I’d much rather the color to just fade away then darken over time. You have a rating of Preventing UV graying at 2 year mark. Would that be applicable when trying to determine how much a stain will darken over time? You rate the TWP 1500 a nine for preventing graying after 2 year mark- wondering if it applies to darkening also. Is the rating as applicable to siding as it is to decks? Thanks for a great site.