Colouring existing pointing

[giltedge]

Just wondered if there is anything I can do short of disc cutting it out to colour pointing that's already be laid between grey slate, the customer wants it darker in fact the darker the better. I tried mixing black pigment with water and brushing it onto the existing pointing to let it soak in but I'm thinking if it rains will it wash out? Any other ideaswould be greatly appreciated. Thanks

[lutonlagerlout]

not really
there is a company called bricktintuk that may be able to do something but it costs

grinding it out is a nightmare

give it a winter and it will get darker with weathering

LLL

[giltedge]

Thanks