Sketching
Marius Ursache - Sketching & Prototyping
POP App for iOS and Android - Turn Sketches into Prototypes
Typography
Scale, sizes, leading - Download sheet
Color
Color Wheel - Available Schemes | How Figma has it
Color Palette - Download Sheet | Contrast Test 1 | Contrast Test 2
Useful resources
Fonts
CreativeBloq - 30 Perfect Font Pairings
Colors
Usecontrast.com Contrast Checker (Figma Plugin) & Mac App