What are your country's rules or regulations for the colors of reflectors or lights? Many countries have rules or regulations that specify what color your lights (headlights or rear lights) or reflectors must be. What are they?

In your answer, please note the country (and state, if applicable) and link to the regulations if possible. 

Related: Reflective tape instead of rear reflector  (Queensland, Australia)
New Zealand

Legal requirements for your bike:


Brakes on front and back wheels (just on the back if it was made before 1 January 1988).
A rear reflector visible from 100 metres when light shines on it.
If you want to ride your cycle on the road during the hours of darkness, it must  have:


one or two white or amber headlights that can be seen from a distance of 100 metres (one of these headlights may flash) 
one or more red rear facing lights that can be seen from a distance of 100 metres  (this may be steady or flashing), and
pedal retroreflectors on the forward and rearward facing surfaces of each pedal (or if the bike does not have these the cyclist must be wearing reflective material).



Your responsibilities 

It’s up to you (the rider) to:


make sure your cycle is fitted with brakes, lights and reflectors that comply with the law
wear your cycle helmet
follow the road rules. 


If you don’t, you could get an infringement fine or be taken to 
court.



What are the ‘hours of darkness’?

Legally, ‘hours of darkness’ means:


any period of time between half an hour after sunset on one day and half an hour before sunrise on the next day,   or
any other time when there isn’t sufficient daylight for a person or vehicle to be clearly visible at a distance of 100  metres.




That's all from the accessible "fact sheet" http://www.nzta.govt.nz/assets/resources/factsheets/01/docs/01-cycles.pdf dated February 2014.

Note the onus is on the rider of the bike to make sure its legal, not the owner should that be different.