Ideas for achieving colour in full shade?

[ImplementingTheDennisSystem]

I have a massive wooden planter that is in full shade all day long. What can I plant in it for a bit of colour?
So far I have fatsia japonica and hardy ferns. I'm going to add a burgundy-coloured heuchera too.
Any flower ideas to add into this mix please?

GW article

I read that article going through old magazines at the weekend

Fuchsia!

I have a Mrs Popple growing in almost complete shade and it’s lovely for colour. Skimmia flowers early doors and I have one called Kew Green which has yellow flowers which smell of honey. Japanese anemones are good for shade as well and come in white and pinks (I have some magenta ones called bressingham-something in shade).

there are hardy geraniums that grow well in shade. also dicentra formosa

My liriopes and astilbes get flowers as well in deep shade.

Pulmonaria is lovely for autumn winter flowers in the shade, and has lovely spotted leaves and a nice dome shape that sets off other flowers during the summer. Lots of the blue/purple tones in geraniums like shade. I also have a heavily shaded corner, and I have a climbing hydrangea that’s thriving in it

Busy lizzies do fine in shade.

Astilbe, Japanese anemone, bleeding heart and hydrangea are all doing well in the shady part of my garden.

Astrantias like shade, so do brunnera and they have lovely bright blue flowers at this time of year. Epimediums ate pretty and like shade.

Thanks so much for these great suggestions.
What I'm going to do is relocate into my planter a little hydrangea that we have in full sun elsewhere in the garden and which is looking very sickly. I'm also going to dig up a clump of Japanese anemones that we have elsewhere in the garden (they are also in full sun and doing well - they must tolerate all conditions). Then I'm going to buy a couple of fuchsia as we're going for a vaguely tropical theme and they will work perfectly with it!