Changing image border colour.

Hello. I've just upgraded to pro and have managed to get my site almost back to how it was before the upgrade. I cannot see how to change the colour of the border around each image (not widget). Before I upgraded the default colour was white, which I liked. How can I change them to white, please? Sorry if this is really obvious. (I found everything else I needed in this forum!) site is being hosted temporarily at www.thebeatsanctuary.co.uk/grant2