Gold is not a color like red or purple. The closest you can get with standard colors is orange, the mix of red and yellow. Adding a little blue will make the orange brown-er and possibly more like gold. Don't try to mix the color. If you are painting, carefully examine the object and see what colors are present. Usually, a gold obejct will reflect multiple colors, shades and tints. Try to get the right values of color for each small segment of the object and paint them individually, maybe with some blending depending on how hard the edge is.