EXTERIOR GREY LIMESTONE NEEDS DARKENING - Tile Advice

[Lorraine]

I have a patio tiled with tumbled grey limestone. Every year I clean it and seal with LTP stone oil, using a small brush to work the oil into the stone and wipe any excess off. This year had it pressure washed which was faster but it looks paler to me. The normal colour is a charcoal grey and it's lighter than that now. I did a test patch of LTP Colour Intensifier and Stain Block but this hasn't done anything for it colourwise (2 coats on a small area 5 hours apart this morning). I am a bit scared to use LTP blackstone in case i end up with 'black' stone instead of dark grey. I could do with some advice as to what any of you might have used successfully to restore colour on faded limestone. I have not used any other brand apart from LTP since it was laid. Grateful for any recommendations you have. Thanks.