Consistency is a one of many UX design principles that’s important to designers to keep it in mind, because that will prove your product to be a good one.
In general, humans have a consistent behavior about decision-making, it’s will be easier to make single decision and stay consistent more than make a new decision every time, and normally human are have limit time to decision and think about new process, if something made them to think or learning for long time, they will be unsatisfied with your product and go away.
That’s why consistency designing should happen in your design, to attract users to your product, and didn’t make them go away with a bad experience. And this is the reason for it.
Learning is a good thing, but not everyone wants to learn something new all the time, as we had said that it's a single decision and staying consistent is always easier for normal users. So the consistent design will help them to reduce learning time and make them process faster, by creating patterns according to their habits and experience.
For example, the button is the one element that will bring users to the next process when they click on it, but sometimes the next process might have multiple choices, like positive and negative. If you design a positive way button to the same pattern like size, color, or shape and stay consistent : they will know at first see that’s will bring them to the next positive steps that they didn’t have to concern that they will cancel their process or destroy their device.
And the negative way button are should be different color (only color) from the positive one to realize them that’s it’s might be cancel your process, delete something, or made something change in your device, normally the negative way button color are usually be red, to consistent with their experience like they seen stop sign, red traffic light, or many warning sign : that’s they can realize that there will be the dangerous way, or the way that’s designer didn’t want they go.
Some buttons are not dangerous at all but designers just didn’t want them to be accessed at all, like back button, cancel, or anything else : they usually use gray color to reduce the attention from users.
Users are tend their own role that’s they experienced, they always expect that’s everything would be as they had predicted, if something breaking their expect they might be have a bad experience of using, and It can be confusing and frustrating for them to use it.
For example, for positive way button we should using the same pattern with another one in project, don’t try to using too much color, that’s will made users confuse about their process and waste their time to learn about it, or did something that opposite this universe like made a positive button be red, and negative one is green that will confuse them at first see and made them to try to read a word in button that’s they shouldn’t have to read it.
