Erik D. Kennedy offers 7 Rules for Creating Gorgeous UI (Part-1): a non-artsy primer in digital aesthetics. His second rule is to design first in black and white, which he likens to mobile-first design:
This is a reliable and easy way to keep apps looking “clean” and “simple”. Having too many colors in too many places is a really easy way to screw up clean/simple. B&WF forces you to focus on things like spacing, sizes, and layout first. And those are the primary concerns of a clean and simple design.
He provides a grayscale wireframe of Haraldur Thorleifsson as an example of such an approach: