The equidistant triad is represented as a equilateral triangle on the color wheel. This means there will be 3 colors in between each of your triad. Most notorious is the primary triad: Red, Yellow, and Blue, then the Secondary triad: Orange, Green, Violet. Tertiary triads: Blue-Green, Yellow-Orange, Red-Violet and Blue-Violet, Yellow-Green, and Red-Orange.
In the following demo we utilize a primary triad. It has a broad value range and is dynamic. Make a 6 pointed star to use as a diagram for harmonies. Shade the points with a black to white value scale , then glaze the corresponding color over. This demonstrates the power and potential of black (and its tendency to “flatten” space).
Blue is dominant in this still-life so blue determines the triadic combo: Blue, yellow and red.
I match a blue to the blue glass. I make a color star first, then map the still-life, then begin lightly layering in shades and highlights. Look closely to notice how the blue changes in intensity throughout the glass. Mix in gray or black for duller areas according to value. Gray will dull the intensity/saturation but will not effect value like black.
I choose 4 gray pencils to try; a light and dark “warm” gray and a light and dark “cool” gray. ( there are many shades of gray).
Try this exercise with other triads. Use transparent, reflective objects for greatest intensity variation.