One thing has always bugged me ever since the Stars set were made, why did they choose to make Takanuva silver and white instead of gold. The books and the comics did show that he was cured and no longer had shadow powers.
How did the set developers forget that he once had gold colors, did they just rush his colors based on his 2008 set?
I assume it’s because the Golden armor should be something special for the wave. Already having a golden character somewhat ruins the aesthetic purpose. Takanuva was not supposed to stick out from the rest, that spotlight was reserved for Tahu.
Aside from Golden Armor being the collectible for the wave, Lego also retired that older style of gold. So to keep costs down, they reused what mask they still had around, which was the silver version of the mask used in the Makuta set.
Which sounds absolutely dumb. Even if that answer was old. Golden armor was. It was only 3 pieces needed on Takanuva, while the Golden Armor gimmick was split between all 6 sets.
When the wave’s gimmick is to have one golden piece in each set, it seems counterintuitive to make one set have three. Quantitatively that’s 50% of the Golden Armor right there. A golden mask especially would have made Tahu less distinct.
The issue wasn’t that the design team had a limited amount of gold pieces to use. The issue was that the gold pieces were meant to have special collectability value, which would be somewhat ruined by including the colour in a standard figure. This would be especially true if the gold pieces were exactly the same as the “collectible pieces”; why would someone buy all six sets to get the “Golden Bionicle” when they can just buy a second copy of one set and get half of the exact same assortment of golden parts?
There’s also the recolour issue; set designers typically have a limited amount of recolours and/or new molds to use, so there’s the possibility that there weren’t enough “frames” to recolour the Avohkii to the new gold.
Story-wise Takanuva masked his Toa of Light identity.
The real world reason was to fill the “white set” slot in the Stars line up.
It is as simple as that. It has nothing to do with his 2008 self.
And as others have pointed out, the Golden Armor was collectible for that year.
Interestingly, the quote that Tukah shared mentions that Stars Takanuva may have had that color scheme because the 2008 set sold better than the 2003 set. But I feel as though that was likely for reasons other than the color scheme—the two sets are quite different…
also there are some 2009 Eljay posts above it 
Set developers have very little story guidance. As other users in this thread have mentioned, Takanuva had to fill the “white set” slot, and not steal the thunder of the “Build the Golden BIONICLE!” gimmick of the Stars wave.
another reason why i think the golden armor should have been for him and not tahu