Question About Color Balance Tool

[Maxume]

Hi

I'm finally (and thankfully) being forced to switch to GIMP but I've just hit my first snag.

I want to adjust the color balance of an image on the master level (in other words, adjusting the color balance on the image as a whole; not shadow, midtones and highlights separately) but the Color Balance tool doesn't have an option to do so.

I'm sure the there has to be some way of doing it on the master level but there doesn't appear to be an obvious way.

Could someone please help?

Thanks