Blue and black: What Color Do They Make?

Blue-gray

Blue + black = blue-gray. With more blue you get denim blue; with more black, charcoal.

More shades from the same colors

Denim blue2 parts blue + 1 part blackCharcoal1 part blue + 2 parts blackLight blue-grayblue-gray + whiteDark blue-grayblue-gray + black

Put the color down first and add black little by little: a little black darkens a lot.
To darken without dulling the color, try a darker shade of the same color instead of black.

What color do blue and black make?

Blue + black, in equal parts, make blue-gray. With more blue it leans toward denim blue, and with more black, toward charcoal.

What ratio of blue and black should I use?

Half and half makes blue-gray. 2 parts blue to 1 part black gives denim blue; 1 part blue to 2 parts black gives charcoal.

How do I make blue-gray lighter or darker?

Add white little by little to lighten it (light blue-gray) or a little black to darken it (dark blue-gray).

Is it the same with watercolor, acrylic and oil?

The result is similar. Watercolor looks lighter because the white paper shows through; acrylic gets a little darker as it dries.