True, both of the red and white phosphorus is a pure substance.
Both red and white phosphorus is made of phosphor element but they have a different structure which causes them to have a different color. This phenomenon called allotropes when a chemical element has two or more different form.They are not compounds as they are only made of phosphorus. A compound should be made by at least two different elements.
Gold has a very high density of about 19.32g/cm^3 while Aluminum has a low density of 2.7 gm/cm^3 which means gold can pack more amount of matter in a comparatively small space as compared to Aluminum.