This section is from the book "Cyclopedia Of Architecture, Carpentry, And Building", by James C. et al. Also available from Amazon: Cyclopedia Of Architecture, Carpentry And Building.
Coloring matter has not been used very extensively in concrete work, except in ornamental work. It has not been very definitely determined what coloring matters are detrimental to concrete. Lampblack (boneblack) has been used more extensively than any other coloring matter. It gives different shades of gray, depending on the amount used. Common lampblack and Venetian red should not be used, as they are apt to run or fade. Dry mineral colors, mixed in proportions of two to ten per cent of the cement, give shades approaching the color used. Red lead should never be used; even one per cent is injurious to the concrete. Variations in the color of cement and character of the sand used will affect the results obtained in using coloring matter.