This is a question I've been meaning to ask for a while and forgive me if it has been discussed here before.
If the same image appears across multiple pages on a website, should the alt tag always be the same or should it vary according to the subject of the page.
I suspect that Google would expect to find the same alt tag everywhere the image appears as the alt tag is supposed to describe the image. But for SEO purposes would it be beneficial to change the alt tag from just "widget" to "blue widget" or "red widget" if the image is on the blue widget/red widget page (assume it is a black and white image!)
Anyway, I'm interested to hear other opinions and more importantly, has anybody heard of a site incurring a Google penalty for mis-describing images in this way?