The $I-V$ characteristic of an LED is:

1. For an LED, the "turn-on" voltage is related to the energy gap $E_g\approx eV$.2. For light emission: $eV=\frac{hc}{\lambda }$.3. ${\lambda }_{blue}<{\lambda }_{green}<{\lambda }_{yellow}<{\lambda }_{red}$.4. Therefore, $V_{blue}>V_{green}>V_{yellow}>V_{red}$.The graph should show the Red curve starting at the lowest voltage and Blue at the highest.