Thermistors' colour coding same as the resistors'?
Thermistors are only a type of resistor in a limited sense.  Within a given temp. range they behave linearly in current.  The packaging of Thermistors varies quite a lot, Glass beads to plastic packs.  As far as I know there is no color coding that is common.  I did a check on Omega and Honeywell's site.  No mention of a color coding there either.  I would think the 18p is a manufacturing code and not an electrical spec.

Also, testing with 30V!!  How big are these things!