Question

which led bulb has a higher forward voltage?

Explanation:

In general, blue LEDs typically have a higher forward voltage (around 3.0 - 3.6 V) compared to yellow (or amber) LEDs which usually have a forward voltage in the range of 1.8 - 2.2 V. This is due to the different semiconductor materials and band - gap energies involved in producing different colored light. The blue LED's semiconductor structure requires a higher voltage to overcome the band - gap and allow current to flow in the forward direction, emitting blue light.

Answer:

The blue LED bulb has a higher forward voltage.