That depends on what you mean by "legal". Amber is the only allowable color for front turn signals as per Federal Motor Vehicle Safety Standard 108, Canada Motor Vehicle Safety Standard 108, UNECE Regulation 48, Australian Design Rules, Japanese Industrial Standards, Chinese GB standards, Russian GOST standards, and probably every other national and regional vehicle lighting regulation. Some US states still have language from the early '60s (1963 was the first year of amber front turn signals in the US), saying that front turn signals may be amber or white. Even if you live where local codes can be interpreted to allow you to run white front turn signals, doing so would be foolish. The reason why amber turn signals came in for 1963 is they're much more conspicuous than white ones, day and night. It would be plain, flat dumb to degrade the safety performance of the turn signals even if an outmoded, neglected state code fails to stop you.
Parking lights (front position lamps) are allowed to be white or amber throughout North America and in some other parts of the world, but front side marker lights must be amber, and on many vehicles the front side marker light function is provided by lateral visibility of the parking light.
Bottom line: if your front lenses are colorless, don't be a dumdum; run amber bulbs.