i know that iron(II)hydroxide is brown solid,how about iron(III)oxide?

Answer 1

The colour of iron oxides vary a lot.
Iron(II) hydroxide in its purest form is white (even though the handbook says it is pale green). We almost always see it in the test tubes as a dirty green. The colour is due to partial oxidation of Fe(OH)2 to Fe(OH)3.

Rust is basically Iron(III) oxide, and is reddish brown to black.