Color is the most significant factor affecting a ruby’s value. The finest ruby has a pure, vibrant red to slightly purplish red color. In most markets, pure red colors command the highest prices and ruby with overtones of orange and purple are less valued. The color must be neither too dark nor too light to be considered the finest quality. If the color is too dark, it has a negative effect on the stone’s brightness. At the other extreme, if the color is too light, the stone may be considered to be a pink sapphire, even if the color strength or intensity is high. That said, pink sapphires enjoy a following at far more competitive prices than rubies. Ultimately, the most desirable color of ruby is the one you prefer the most.

Source: GIA