Seems easy, if you can go out in the daytime. I had a quick rummage through my recent pictures though, and this is one of the most vibrant, but I can only see three vibrant colours!
Same with some of my other colourful photographs; three seems easily attainable, four maybe a bit of a challenge.
Haven't been near Christmas colours yet, so that might be easier.
I suppose you can always take someone along in a bright coat, or with some other vibrantly coloured item and place that person in the scene!
My workmen in front of a Christmas display might well do the trick.
And no, I'm not participating yet! Still too much going on!
