After leaving school I was a tyre fitter for many years and during the years fitted pretty much every type of type of tyre from private car of course through to commercial trucks (both split rim and tubless/super singles etc.), fork lift trucks, agricultural and one we're all interested in here- motorcycle for both race (hand cut slicks -remember those? I also re-grooved truck tyres for those loving the rubber smell) and road.
Admittedly things have changed quite a lot through manufacturing and quality control etc.
But yes the simple answer is the coloured dot indicates a light spot in the tyre construction and ideally should be placed by the valve if the fitter knows (you'd be surprised how many don't) or can be bothered.
However, just to confuse things, sometimes there would be two coloured dots and as I always understood it, a yellow dot indicated the light spot of the tyre and if the fitter knew/could be bothered this is the one that should be placed by the valve.
Along with the yellow dot there would also be a red dot which indicated the radial run-out -tyres were never quite perfectly round and as nor were (are?) wheels so they too would be marked with an indent to line this red dot up to equal things out as much as possible. This point in the tyre was (and possibly is still) less known about - try asking a fitter and see what they say.
There are a lot of factors to be taken into account when balancing wheels such as, (the already mentioned) sprocket carrier and brake discs which will all contribute to a frequency vibration at a given speed.
Personally I balance mine myself wheels fitted into the bike with the discs but calipers removed for the front, the rear is trickier as to use the same method the chain also needs to be removed.
Of course this is really only a static balance as opposed to a dynamic process using a machine but I have never suffered any wobbles on road or race bikes.
https://www.google.co.uk/url?sa=t&rc...ZBI6vQP3OVv2BG