A 100 Ohm resistor acts as a guardian angel for white, blue, and green LEDs powered by 5V. It limits current flow, preventing these LEDs from being overloaded and potentially burning out. While it can work with other LED colors, the brightness might not be optimal due to a mismatch in resistance needs.

The color code for a 100 ohm resistor is typically brown-black-brown-Gold. The first digit (brown) represents 1, the second digit (black) represents 0, and the third band is brown again, which signifies a multiplier of 10 (one with one zero). The fourth band (gold in this case) typically represents the tolerance of the resistor, indicating the allowable variation from its stated value. However, for many 4-band resistors, the tolerance is implied to be ±5%. So, the value is 10 * 10 = 100 ohms.