To complete the color Standard - the designer should propose a tolerance. Before we start we have to learn more about color difference formulas. 

Typically the color difference is described by the ∆E formula. Today there is dozen of variants - but the current standards in the Graphic Industry mostly use ∆E 2000.  At the same time in Textile Industry ∆E CMC is still in use. A lot of variants come from the situation where is no ∆E formula that corresponds with us as we perceive the color difference. Numbers in some situations seem to be inadequate to how we see the difference. But from another hand to create contracts we need to use numbers instead of personal emotional feelings about color differences.

∆E 2000 

As mentioned not perfect but the most common way today.  A smaller one is better, but don't expect zero! Even the value of one is not realistic.  Take also into account that all values above 10 are loses precision. If something is higher than ten - in fact, it doesn't matter how much - the difference is definitely too high.

To learn more about ∆E 2000 and other formulas ChromaChecker has created a series of tools that helps users practically learn these differences. With the limitation of displays, we can get some personal experience which is a key skill for specialists working with color.

→ Spot Color Exercise

When performing exercise it is important to observe:

• How different formulas change values
• How behaves different sets of color samples (neutral, mid-saturated, vivid...)
• Influence of sample isolation 
• Influence of exercise background ( white, warm white, grey, black, colorful)
• time and personal condition ( level of relaxation, time of the date,...)

 Execute Spot Color Exercise

→ Image Color Exercise

∆E formula is designed to compare two samples. If one image has to be compared with the second one ChromaChecker defined a formula that is 95% percentile ∆E2000 - which statistical approach where every single pixel is analyzed and compared, 5% worse results are eliminated and the value for lat 95percentile quantifies image difference - We call this variable E-Factor

 Execute Image Color Exercise

→ Personal E-Factor

Before you set expectations you have to agree that for most situations a given level of tolerance has to be accepted. The Personal E-Factor is an exercise where we are not checking if differences exist - what is obvious - but if we agree to accept them. series of pairs of images randomly change color shift keeping the ∆E value on the value that is defined by the algorithm.

Execute on-line Personal E-Factor  — display version. Order Personal E-Factor printed version.

→∆E Variator

If your display is calibrated and profiled - and ∆the E formula is selected - there is a very practical tool created by ChromaChecker that produces for a given value.