Usability. UX and UI design without defining and setting usability standards is slippery slope into a world of hurt for you and your user.
One of the biggest fails in UI design is when there is not enough contrast between the type and the background color of the component it is on. The background for type be a button, a nav bar, the content area... essentially any where or in any form type is displayed. Not only can it make for a not so great to impossible experience for user especially if they have any type of visual impairment, but it can bring legal problems to developers and business.
As a graphic designer working in the industry of interactive design it is important to learn about Web Content Accessibility Guidelines (WCAG) and how they should influence design decisions in the craftsmanship of user interface graphics.
One of my favorite tools out there to check the if the contrast of my UI components will pass an accessibility are contrast checker apps. There are many web apps and mobile apps out there for this purpose. Take a look at this example, I wanted to test the contrast usability of this button color scheme combo:
So I sampled the color of the text and the background color with an eyedropper tool to get the numerical value of each color and then popped each color value into Userway.com's nifty contrast checker web application.
Not only does it tell me that this particular turquoise and yellow color combo fails for enough contrasts it also supports it's rating with more visual examples that automatically produce under the resulting contrast ratio.
As a UX / UI graphic designer this is one of the many areas of usability that need to be researched to make smart design decisions. The success and longevity of interactive products must take into account the behavioral and functional aspect of the experience. The first place to get that wrong is with poor contrast. Designing for usability for a variety of users including the visually and or hearing impaired is an essential skill for an interactive digital product designer. This U, for usability plays a major role in the success of UX / UI projects.