Typically three bands with colors that encode numeric values. The first two bands are two digits of the value. The third band in the exponent or number of zeros to add to the value. The fourth band indicates accuracy using Red +/- 2% Gold +/- 5%, Silver +/- 10%, None +/- 20%. The values of the first three bands are color encoded as follows:
value color 0 Black BLK 1 Brown BRN 2 Red RED 3 Orange ORG 4 Yellow YEL 5 Green GRN 6 Blue BLU 7 Violet VLT 8 Grey GRY 9 White WHT
When indicated on a schematic, Resistors are often labeled by "R" and a number. E.g. R10 is the tenth resistor. The value will typically be specified with 2 or 3 digits of accuracy in engineering form (e.g. 2.3, 230 vice 2.3x102, or 43 vice 4.3x101), a multiplier (k, M, or none), and the Ohm sign. On European schematics, the Decimal point may be replaced with the multiplier and "R" used when no mutiplier is used. Eg 10R = 10 Ohms, 4M7 = 4.7 MOhms, 0R1 = 0.1 Ohms. In this case R10 may indicate a 0.1 Ohm resistor (in which case it should have been written 0R10) or the tenth resistor on the schematic.
See also