Visual Design
When you say Visual Design in reference to digital products, you’ve said a mouthful. Did you mean the colors? The layout? Or the imagery? Font is an important UI consideration but typeface sensibilities originate in print. As do logos and color schemes. What about animation? Can a Graphic Designer do it all? Should they? Visual Design as it relates to software breaks down into three overlapping sub-disciplines: Graphic Design, UI Design, and Motion Design.
Graphic design
Graphic Design was a discipline long before anyone thought phones should do anything more than make phone-calls. Graphic Designers were making choices about color, typeface, imagery and layout before the printing press.
UI Design
UI Design is not UX Design. User Interface Design is essentially Graphic Design as applied to any interactive, electronic conceit, like a Web page. Because UI Design is the most conspicuous part of UX Design, the two are often conflated.
Motion Design
In the context of digital products, Motion Design describe changes in the User Interface over time. It encompasses considerations such as sequence and timing. It happens when a menu slides down or a YouTube video plays.