This value is displayed in different ways and there are currently two standards for measuring how resistance appears with either color-coded markers or SMD codes. Try out our Resistor Color Code Calculator in our Tools section. How To Read Resistor Color Codes Arrow Com Color Coding Coding Basic Electronic Circuits Resistor Color Coding uses colored bands to quickly identify a resistors resistive value and its percentage of tolerance with the physical size of the resistor indicating its wattage rating. . For very small electronic components a color code instead of printed text is used to indicate the value rating or and tolerance. A resistors number of bands might range from three to six. The capital letters represent the first letters of the colours and their positions the digit values. Resistor color codes always have digits followed by a multiplier follower by a tolerance value. Brown Green Silver would be a 15 Giga Ohm