Set a CPT slug as a base name for all the taxonomies

I think if you change the rewrite in your register_taxonomy $args

'rewrite' => array( 'slug' => 'photographies/couleurs','with_front' => false  ),

This will probably clash with rewriting the custom post type so you’ll more than likely get a 404 on this url: http://thewebsite/photographies/ but if you don’t need that url then this solution will help you get closer to what you want but I’m pretty sure: http://thewebsite/photographies/couleurs/ will always give you a 404 as within a taxonomy you’ll need to create terms then you can link to a page with those terms e.g. http://thewebsite/photographies/couleurs/black-and-white.

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