Repointing Sandstone wall

I need to repoint my garden wall, which is sandstone blocks with a rounded coping stone, which I am going to replace with reclaimed sandstone coping stones.

Not sure if I can just crack on with a standard mortar mix or does it need to be a lime mortar? The wall is circa 1900 although sure its been repointed before now - not sure what the current mortar is?

Also, if I use a modern mortar mix, I dont want the mortar to be bright grey in colour - is it easy to mix a colourant?

I think that using a cement based mortar may not be the way to go...

Sandstone as a walling material does decay over time and what you need to do is inhibit the deterioration as much as possible. Cement based mortars are not as plastic/flexible as lime based, also lime based mortar is quite porous (as compared to cement based) and allows the wall to 'breathe'.

Repointing a sandstone wall with cement mortar will trap moisture and mineral salts in the structure causing the sandstone to deteriorate excessively.

thought that might be the case.

Is lime mortar fairly easy to use? Similar to modern mortar, which I have used previously.

Also, am I likely to be able to Lime mortar at one of the big sheds, or better off at a merchants?

cheers

Definately a decent merchant for that one. Also mixing colourant into cement is often difficult to get consistant colour between gauges unless its preprepared thouroughly and mixed up as needed.