funny thing with mortar sand. We have off-white mortar, to get it that way they used white sand (it actually looked yellow to me but they classify it as white so don't panic when you see a pile of yellow sand outside your house mixed with white cement.
But then when our brick fence went up (different builder), they used grey sand, still mixed with white cement but I am assuming they mixed it in different strengths or whatever, cause the mortar colour looks just the same! strange but true.
Just thought that was interesting.