Matt D. Smith publishes Shift Nudge — a paid interface-design course that has become one of the most highly-regarded resources in the modern UI / product-design education market. The course focuses on the visual craft of interface design at the level of pixels, type, and color.
His CourseFlix listing carries the Shift Nudge course. Material is paid and aimed at designers and developers ready to take the visual craft of interface design as a deliberate skill.