Most modern designs can incorporate many accessibility principles without serious sacrifice. Of course, some past design habits don't fit well in an accessible web:
- Your site will use color to complement, enhance, or highlight information, rather than convey this information primarily (or exclusively) through color.
- Your design may employ subtle visuals and transitions, but overly subtle differences between backgrounds and texts (for example) are discouraged.
- Visual queues (like element outlines) are not to be tossed away simply because they appear to disrupt the surface a little. You're better off finding a way to make these queues stylistically consistent with your design, rather than dumping them altogether (as is currently the habit on many sites). Alternatively, allow users to enable these queues with accessibility widgets.
- Some ultra-modern designs (like form fields without labels or borders, or like instructions that only become visible upon hover) should be avoided.
Ultimately, accessibility compliance will impact your design by simplifying it. Nevertheless, wherever you feel simplicity is costing you too much because your brand happens to need certain sleekly modern flavors, you can still accommodate both your own preferences and the demands of your accessibility commitments by including widgets that cater to users with special needs by simplifying the user experience as required.