So I was browsing on the Winx Club Web and then I found this.
Bloom:
Stella:
Flora:
Musa:
Layla:
Tecna:
What do you think? Strange. >_<
No wonder, Stella's gone green in Season 5, they changed her favourite colour. I don't really mind Flora's. Musa's gone yellow! I always thought it was red or blue. Tecna's is okay, but you'd think it'd be purple or green. OMG! Tecna and Layla have the same favourite colour! No comment on Bloom's, when you live with red, it'll eventually, turn into your favourite colour.
Source: http://www.winxclub.com/ Just click on he link and click on any of he Winx Club members at the top and you'll find out their fav colours.
I'm not really sure this has any credibility since I don't think they ever talked about favorite colours in the show. Unless it is from the official website of course.
I'm not sure if this is true...but I remembered in Season 2 and also the Special mentioned Bloom's and Flora's favorite color was purple? =S
Could be possible they changed their favorite colors as the Season goes by...I always thought their Winx Outfits were their Favorite Colors! xD (Bloom - Light Blue, Stella - Orange, Flora - Pink, Musa - Red, Tecna - Purple, and Aisha - Green)
So it's from Official Winx Club Site, then that's the true source. =)
Just like us, we changed our favorite colors. Right? ^_^
Yep between black and red constantly. Although I just cannot see that being correct as they seem a little strange apart from Flora.