In some Eastern cultures, white is considered a proper mourning colour.
In Western Christian tradition, it generally is not, except as an accent colour (the one exception being that it is acceptable for royalty to wear unrelieved white for mourning.) Generally at a Christian funeral, the expectation is that clothing will be dark and subdued; no loud patterns and no bright cheerful colours. It is also best if it is modest: nothing too low-cut, nothing risque, and no shiny bling trim, such as sequins or beads.