You're most likely to encounter SketchUp's color picker when you apply materials to a model. (However, you do find the color picker elsewhere, such as when selecting a color for text.) This article explains how to use the color picker for your current operating system. To select a color, you can choose from the following different methods:

SketchUp’s Match Photo feature has inspired many happy dances, because it enables you to

Have you ever stuck a decal on a window or a wall? In SketchUp, sticking an image on a face is even easier than those decals, because digital images don't wrinkle or trap air bubbles. Technically speaking, SketchUp enables you to import images that are already on your hard drive. When you import images from your hard drive (select File > Import to see the Open dialog box, shown in the figure), you can import the image as an image, a texture, or a matched photo.

To add detail and realism to your models, SketchUp enables you to paint materials on faces. Materials are essentially paints that have a color and optional texture (defined within an image file). For example, in the following figure, the roofing material has a blue color and a texture that simulates metal roofing. The siding and grass are also materials that have a color and texture.

With colors, textures, and photos, you can add details that make a 3D model look realistic and complete: Colors are like paint. Textures add realistic materials, such as carpet, tile, grass, wood, glass, and anything else you can capture as a digital image. Photos can be pinned to your model (or just a face within it). In SketchUp’s Materials panel (Microsoft Windows) or Colors panel (macOS), you find predefined colors and textures, which you can edit. Or try mixing your own colors or creating a texture from a photo.