Amane Misa has been known to have quite different shades of blonde in different mediums; if you are striving for accuracy, it depends on which Misa version you're doing.
Here are some reference pictures.
1) Generic manga version: Orange-ish blonde
2) The popular manga illustration: VERY orange
3) Anime version: Lighter blonde
There are probably more versions / more blonde shades of Misa (in artbook illustrations), but those should give you some ideas for now, since they seem to be the most popular ones amongst Misa cosplayers. Hence the wig that looks more "Misa-ish" depends on whichever one of the versions that you decide to do. Some Misa cosplayers also mix-and-match (like they take the anime hair to go with a manga outfit, etc).
That's one of the advantages of picking a Misa wig - the exact blonde shade could be relatively subjective to the cosplayer, so it's most likely okay for you to pick the exact shade of your liking. Good luck!