|No Color||-||-||+/- 20%|
Four color bands
The first two colors represent significant digits, the third is the multiplier. The fourth band is the tolerance of the resistor value. For example, a resistor with four band marking red-brown-yellow-gold would have nominal value 21 x 104 = 210,000 ohms (also written 210K) but whose actual value should be within about 5% (gold band) of this number. Sometimes you see a resistor with only three bands, this means the fourth band is no color.
Five color bands
The first three colors represent significant digits, the fourth is the multiplier. The fifth band is the tolerance of the resistor value. For illustration, a resistor with five band marking red-brown-green-orange-brown would have nominal value 215 x 103 = 215,000 ohms but whose actual value should be within about 1% of this number.