We can define colorfastness as, having color that will not run or fade with washing or wear. That means characterizes a material's color's resistance to fading or running. Clothing is colorfast if its colors and dyes do not bleed or run from the clothing. Clothing should be tested for colorfastness before using any type of bleach or bleaching solution, or strong cleaning product. Colorfastness is very important factor for buyer. Colorfastness properties of textiles are an important measure of quality of a product.
Colour fastness can also refer to how it holds up to light such as sunshine or artificial lighting. Another type of colour fastness refers to how well it stands up to frequent washing. These you can check out yourself but it will take a bit of time.
You can take a small swatch of the fabric in question, cover part of it with a solid material such as a piece of cardboard or similar and place the swatch in a sunny south or west-facing window for a fairly long time. Check it occasionally by removing the block and see how much the remainder of the swatch has faded compared to the covered section.
For wash fastness you can cut two swatches of fabric. Place your control swatch in a drawer. Wash the other swatch in hot water with detergent in your washer and then dry in the dryer as many times as you wish. Comparing it each time with your control swatch will show you how the colour bears up to washing.
The most effecient way is that we can check the color fastness of a fabric by running a test. The test methods that we usually use for Crocking/Rubbing are called "BS EN ISO 105 X12" and "AATCC 8". We need a Crockmeter to carry out this test and below is how it typically looks like.
During the test, a white conditioned rubbing cloth would be rubbing on the test specimen, back and forth in a straight line for 10 cycles with downward force. Usually, two tests would be made, one with a dry rubbing cloth and another with a wet one.
Then, after the test is done, the tested rubbing cloth should be evaluated against the grey scale under decent light source.