Over the last ten years or so there have been a lot of retailers pushing sets of plastic poker chips as the popularity of poker exploded. Do to mass marketing, these sets all had the same basic colors. These sets consist of white, red, green, and black chips. Sometimes, blue chips were included as well.
As a general rule, these colors fits the standards that most people would set for poker chip colors. White is generally used as $ 1 chips, red as $ 5, green as $ 25, and black as $ 100 chips. If blue chips were included, they were normally $ 10 or $ 50 chips, which is unusual because these denominations are almost never used in casinos, whether it be cash games or tournaments.
However, there is no worldwide standard color scheme for poker chips. Not only that, but within a country or even area of a country (such as Las Vegas or Los Angeles), the colors can vary from casino to casino.
Let's start with the easiest colors -
$ 1 - Mostly white, but blue is a common color for $ 1 chips, especially in Las Vegas.
$ 5 - Red
$ 25 - Green
$ 100 - Black
$ 500 - Purple
The colors above are almost universal, although note that the $ 1 chips can be either white or blue. When people are thinking about getting a set of custom poker chips I always recommend blue for the $ 1 chips. White chips tend to show dirt and grime easily and since they are the poker chips used most often in many games, you do not want the $ 1 chips to be very dirty looking.
Any other denominations can vary a lot, especially with higher denominations. Here are some more colors, though these are not nearly as standard as the $ 1, $ 5, $ 25, $ 100, and $ 500 poker chips:
$ 0.25 - Most often blue or red
$ 0.50 - White, Red, Blue
$ 2 - Yellow
$ 2.50 - Pink, which is very popular in East Coast poker games
$ 10 - Blue
$ 20 - Gray or Yellow
$ 50 - Orange
$ 250 - Pink
$ 1000 - Burgundy, but commonly Orange
$ 2000 - Light Blue
$ 5000 - Brown or Gray
Now, the most important thing to remember when you are designing your own set of custom poker chips is that you do NOT have to follow any standards for your own chips. If you want your $ 1 chips to be purple then do it!