It comes courtesy of Jamie Jones, an extra/acrtress/spy on the movie, who has tweeted some inside information about Electro's costume. Unfortunately the original tweets have been deleted, but Jones revealed:
His face & hands are silvery-grey. Eyes silvery blue. He's not in the green & yellow suit yet, but feeling his powers now.
It's interesting that Jones claims that Foxx hasn't donned the green and yellow suit "yet", because earlier rumors coming from the set suggested that this Electro would be closer to the Ultimate version. In the Ultimate Marvel universe Electro wears a black leather outfit as opposed to a garish yellow and green ensemble, which I imagine would fit better to this movie's more grounded, real-world aesthetic.
Fingers crossed that Ms. Jones hasn't been silenced by the studio execs for leaking information and she sends us some more juicy updates soon.