Personaly would never paint a pation it never looks great and the paint will eventually crack/flake off.
I would jet wash it and then put a moss and weed killer down and after about 6 weeks respray the moss killer. If you have trees/bushes over hanging the patio chop them back it will help.

Wallpaper it.

Your problem is that have jet washed your patio, that takes of the glaze off the slabs, so they gets dirtier quicker.
There is nothing available to make them like new again, a water seal may help, but you have no chance of putting any colour down.
Patios get dirty from earth leaking onto them in heavy rain, try running a gulley between the grass/earth and patio.

C. Brewer & sons(decorators merchants) do a trade quality floor paint for external use.
pretty sure its only dark grey available.
surface must be clean & fully dry.
1st coat thinned with white spirit another 2 coats full after that.
We've used it a few times on external areas such as pathways and steps to communal front door.
hard as nails & will last.
satin finish.
approx. £50-£60 5lt

'Bradite' I think ?

Edited by kingdowieonthewall (18 Mar 2017 2.28pm)

Kids,tired of being bothered by your pesky parents?
Then leave home, get a job & pay your own bills, while you still know everything.