That is a big area to touch up. I use my touch up paint for the inevitable rock chips you get up front. You can always try to do it yourself though.
For touch up paint what you need to do is go to the dealer. They can look up your car color by your vin number, but if it is white it should be "Alpine white". You can look under the hood on the drivers side of the engine bay and it should be printed on their too. It comes with a bottle of paint and a bottle of clear coat. Usually runs around $20 I think for both bottles. I also think they sell something to use to run over the paint too to smooth it out, so it doesn't bubble. You may look into that with such a big area.
Otherwise you can go to a professional paint place. I had a 1 1/2 by 5 inch scrap on my bumper from the previous owner and got that repainted for $70. It looks perfect that way of course. My scrap was bigger, but your may be ina more noticable place.
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