Why it matters: It's not a fixed rule and sometimes, for specific cases, more than three primary colors can be used. However, keep in mind that combining three colors is already difficult, so combining 4 colors and more should be avoided.
How to test it: Check your product's color palette. You need to make sure that it has no more than three primary colors.
Look at the example below:
Here’s also an article for you to read:
The Impact of Color on Conversion Rates
Color is one of the most powerful tools in a designer's toolkit. It can draw attention, set a mood, and influence a users' emotions, perceptions and actions. Color does not add a pleasant quality to design - it reinforces it. Pierre Bonnard Did you know that color accounts for 90% of the reason why you purchased a specific product?