The Select & Spray tool lets you try new color schemes in the block by changing all similarly-colored patches at the same time. With this tool, you need to click on the block first to select the patches you want to recolor, and then click on the fabric or color in the palette.
These patches will stay selected while you scroll through the fabrics and colors letting you see several possibilities very quickly. To deselect all the patches, click anywhere on the worktable outside of the block.
Click the Select & Spray tool.
Click on a patch in the block you want to recolor. All patches colored with the same fabric or color will become selected.
Click on a fabric or color in the palette to change the color. Use your mouse to click individual colors, or drag the scroll bar in the palette and watch the block change colors as the selection changes in the palette.