I have a a couple of cheap packs of resistors in E6 and E12 series. The construction is not specified, but I have been assuming that the blue ones are metal film and the tan ones are carbon film. Is the body colour actually a reliable indicator of the construction or do I have to do some tempco measurements to know for sure?
cheap chinese no-brand resistors, even 1% tolerance ones, drift like a surfer on a heat wave
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If you have a 4-1/2 digit multimeter you can see that the small current used to measure resistance is enough to quickly change the resistor value.
Most metal film brand resistors usually do not change more than a digit even if you breath on them and even if you use a 4-4/5 multimeter.
Of course if you need resistors just to regulate the current through a led, that is not relevant.
Carbon film resistors usually drift much more than metal film, so you might check that to tell which is which.