ScriptableRenderPipeline/com.unity.shadergraph/Editor/Resources/Styles/Controls/ColorRGBSlotControlView.uss

ColorRGBSlotControlView {
    flex-direction: row;
    align-items: center;
}

ColorRGBSlotControlView > ColorField {
    width: 41;
    margin-left: 0;
    margin-right: 0;
}