look up the bulb on your owners manual (9005???) and get something like it in platinum or hyper white from headlightbulbs.com.
i just did my fogs and DRL's / hi-beams in 9005 and 9006 yellow bulbs from them.
*note: i have a WRX, NOT a Legacy though. you will have to get the bulb numbers and check your wattage because the 5th Gen Legacy is NOT listed. FYI.