What colour precipitate do aluminium, calcium, and magnesium ions produce with sodium hydroxide solution?

When aluminium, calcium, and magnesium ions react with sodium hydroxide solution, they form a white precipitate. This occurs due to the formation of insoluble hydroxides that do not dissolve in water.

For aluminium ions, the reaction typically leads to the formation of aluminium hydroxide, which appears as a white precipitate. Calcium ions also produce calcium hydroxide, which is slightly soluble in water but can create a white cloudy appearance in higher concentrations. Magnesium ions similarly form magnesium hydroxide, which is less soluble and results in a white precipitate as well.

This is in contrast to the other colors mentioned. The blue precipitate is often associated with copper(II) ions, while the green precipitate can result from iron(II) ions. The yellow precipitate could be indicative of lead(II) ions or other specific reactions, but it does not apply to the ions in question here. Thus, white is the demonstrably accurate color for the precipitates formed by aluminium, calcium, and magnesium ions in the presence of sodium hydroxide.