If you experience dark and flat colors when you print to your Canon Selphy from Adobe Lightroom, don’t worry. There is a easy solution to fix this problem.
You need an ICC printer profile. And you need to activate it in Lightroom.
Tested on a Canon Selphy ES-30 (but should give same result on older models)
Here is what you need to do:
You should have a photo printed by your Canon Selphy that has the right colors and the right contrast.
Hope this helped.
And if you want to read more about ICC profiles then follow this link International Color Consortium.
I have found an ICC profile for the Selphy CP720. I do not have that model but maybe you do and is this file helpfull. Use the file following the method described above.
Download the profile Selphy-CP720-OK.icc.