Mix equal parts of blue and red paint
Add a small amount of yellow to deepen the mixture
Adjust with more blue or red until the shade is black
If using light (LED/screen): turn down all colors to minimum brightness
For printing/ink: combine cyan, magenta, and yellow in the darkest proportions and reduce/add black (K) as needed
For charcoal/graphite: use pure black charcoal or graphite and blend with a blending tool
For dye: start with a dark base dye and add black dye gradually until the desired shade is reached
For fabric/paint: test on a scrap piece first and let it dry before final adjustments