There are several types of multi-color white LEDs: di-, tri-, and tetrachromatic white LEDs. Several key factors that play among these different methods, include color stability, color rendering capability, and <answer>luminous efficacy</answer>. Often, higher efficiency will mean lower color rendering, presenting a trade-off between the <answer>luminous efficacy</answer> and color rendering. For example, the dichromatic white LEDs have the best <answer>luminous efficacy</answer> (120 lm/W), but the lowest color rendering capability. However, although tetrachromatic white LEDs have excellent color rendering capability, they often have poor <answer>luminous efficacy</answer>. Trichromatic white LEDs are in between, having both good <answer>luminous efficacy</answer> (>70 lm/W) and fair color rendering capability.
What is a factor that may be different in the various types of multi-color white LEDs?
luminous efficacy