Unless I am very wrong there's no option to Authomatically extend colours for the bleeding.

Of course to print and crop is necessary to add bleed and that involves placing images or extending them out of the margin.
How is it possible, coming from the company of photoshop, that a function so simple, yet so important is not possible in indesign? It's as easy as extending any color touching the margins of the document to the bleed: copying pixel color information perpendicular to the document.

Of course the possibility of doing it manually should stay, but this feature is a must, as it is a headache to fix this when you have to use documents imported from elsewhere which you cannot modify in the source anymore.