The color of iron is generally a dark gray or black. Therefore, the color for an iron planet could be described as dark gray or metallic black.

A desert planet covered with iron oxide would likely have a reddish-brown color. Iron oxide, also known as rust, gives a distinctive rusty red color to surfaces where it is present in abundance. Therefore, the desert planet would have a reddish hue due to the iron oxide covering its surface.

A desert planet covered with nickel oxide would have a greenish color. Nickel oxide is used in ceramics and glass to produce green colors, so it's likely that the presence of nickel oxide on the desert planet's surface would give it a greenish tint.

On a desert planet covered with iron oxide, the oceans would likely have a reddish-brown color. Iron oxide, commonly known as rust, is responsible for the reddish color seen in many desert landscapes on Earth. If this iron oxide is also present in the oceans of the desert planet, it would give the water a similar reddish-brown hue.

The oceans of a desert planet covered with nickel oxide would generally have a bluish-green color. Nickel oxide is commonly used to produce green colors in ceramics and glass. If the desert planet's oceans were covered with nickel oxide, it would infuse the water with a greenish tinge, giving them a bluish-green color overall.