Not all of Decklinks support LUT’s. Go to System Preferences>Blackmagic Design>Processing>Output Processing. If there is a “Lookup Table” button and it is not grayed out you’re lucky. The list of supported formats and other details are in the manual. Sorry, I don’t have any relevant hardware at hand at the moment.
Another option is to go to you monitor menu and if there is gamma adjustment crank it way up. Boost saturation a bit too.