I have never seen any regulation in NV requiring a certain color of chip. Denoms $1 and under can be many colors in NV. The industry in has pretty much standardized chip colors higher than $1, this could be a combination of the manufacturer/vendor and the individual property. This kind of follows the trends across the country as many jurisdictions require standard colors and they tend to follow the manufactures/vendors leads.

2.50's are generally Pink (Missouri they are not pink because .50 are pink)
5's are generally Red
25 are generally Green
100 are generally Black
500 are generally Purple
1000 are generally Yellow/Arc-Yellow/Orange
5000 are generally Grey

There are possibly some exceptions to the rules but over the years the colors are pretty standard