focalboard/webapp/src/styles/shared-variables.scss

:root {
    --center-channel-bg-rgb: 255, 255, 255;
    --center-channel-color-rgb: 63, 67, 80;
    --sidebar-bg-rgb: 30, 50, 92;
    --sidebar-text-rgb: 255, 255, 255;
    --button-color-rgb: 255, 255, 255;
    --button-bg-rgb: 28, 88, 217;
    --button-danger-color-rgb: 255, 255, 255;
    --button-danger-bg-rgb: 210, 75, 78;
    --link-color-rgb: 56, 111, 229;
    --error-text-rgb: #d24b4e;
}