Which mortar do I need, and how do you match the color?

[ulfben]

I need to put back the stones we took down in our recreation room (built in 1969), see photos. What mortar should be used here, and is there any chance of color matching the new mortar with the original?

I tried mixing some Finja Murbruk B but it turned out noticeably more brown/red than the light gray joint we have.