I'm having a hard time with obtaining the post-game mega stones in Pokémon Y. I have beaten The Champ and rival many times & my ring has been upgraded. I have been looking daily between 8 and 9pm in their proper places. I think these stones appearing may be a one time deal unless the times are different in version Y.
Pokémon Y megastone problem
pokemon-x-y
Related Solutions
Here is a picture from (what I think is) the official Pokemon X&Y Guide.
Every little thing you do in Lumiose City adds to your style. Stylishness brings all kinds of rewards, such as meeting various characters, getting discounts, and unlocking facilities and fasions.
Good luck fellow trainers :)
After more experimenting, I managed to stumble over the answer. For future reference, I'll just post it here.
The regular red mode allows you to tap a Pokémon to bring up the menu (Move, Summary, Item etc.) while blue does not; it's used exclusively for moving. More significantly, when using button controls, selecting a Pokémon in blue mode skips the menu and immediately prepares the Pokémon for moving.
Best Answer
So I found all the mega stones in my game through this video (Except for the X version exclusives). Easy to follow, just pause the video at some places so you can fly there to get it. Only hard ones to get is Alakazite and scizorite.
Also, If you didn't already know,
Houndoomite, Aggronite, and Heracronite are all found in version Y. Although the pokemon corresponding to these stones are found in version X.
Manectrite, Tyraitarite, and Pinsirite are all found in version X. Although the pokemon corresponding to these stones are found in version Y.
I wouldn't reccommend trading your version exclusive mega stones for the other ones, since you can only acquire them once in the game.