I have one background texture that is a wood grain, and I have a menu hover background colour that I would like to match the overall tone of the texture as closely as possible. Using a tool such as ColorZilla, or something similar, can I get an 'average' colour of the texture?
Most graphics packages allow resizing the image, with the required averaging out of the colours. So, resize the image to a single pixel, and 'pick' the colour that results.
I don’t know about ColorZilla, but graphics software like Photoshop, Gimp, paint.net, etc. should all have a filter function that takes any image and computes the average color from all pixels.
Here is a website that does the same: http://www.wisegeek.com/how-can-i-find-the-average-color-in-a-photograph.htm
I think there's an average filter in photoshop, under the blur category or something. You can color pick the resulting color to find out what it is.