How can I detect when a figure's colormap is changed?

The most obvious way to change a figure's colormap is via the Edit/Colormap... menu, although controls such as those added with lutbar are even handier.

How can I detect when the colormap of a figure is changed? Ideally I would even detect programmatic changes such as

set(gcf, 'Colormap', lines)

although this is not essential.

Other figures contain plots coloured coded to an image shown in the main figure, and I need to cascade any changes to the colormap.