A tip for cosplayers (from a fanartist)
A big problem that I've noticed since I've started to follow more the world of cosplay is "What exactly is the best color for wig/hair and eyes for ______________?". I myself am no big expert on such matter, as I do not cosplay much, but I do have some points to share with my fellow cosplayers, from the point of view of an illustrator.
First, if you are using colored illustrations made by the mangá artist. Most commom media used for mangá colored illustrations are copic markers and watercolor. Both of them work with "soft colors", meaning even dark colors like dark brown hair or dark blue outfits may be colored very lightly, depending on the artist's style. A good way to check this is checking Hiromu Arakawa's work in acrylics and her works in copic markers, you can sense the density of the color of the acrylics is much heavier than in works made with copic markers.
Hence, you should be careful to not end choosing a color TOO LIGHT. But how you should know the right color? Well, you need to have a bit of common sense of what "looks natural". It's not because the artist used a FUCKING BRIGHT YELLOW that you should buy that ugly neon yellow wig, buy a blond one! Also remember that to create the illusion of profundity we use different shades and tones for the same color. Pick the intermediate color between the lightest and the darkest shade of the hair you see in the reference illustration you've chosen and you'll probably get what is the actual color of the character's hair. But remember, use your common sense always, this does not work 100% of the time.
Another tip particular for characters with dark hair is that they usually have lighter hair in watercolor/copic marker illustrations than what their hair should look like in real life. If you KNOW the character has very dark hair but the mangá shows a pic of him with... well, brown/blue/purple/green hair you should consider twice before using light brown/blue/purple/green: does it look natural on you? Does it make you look like the character indeed?
Now for those who use acrylics/cel shaded (anime)/pastel illustrations for reference: Some characters that have BLACK HAIR sometimes appear with colored highlights. THAT DOESN'T MEAN THE CHARACTER HAS BLUE/GREEN/(insert color here) hair, it means he has black/very dark hair that when exposed to light will show a faint colorization inclined for said color. Check Rurouni Kenshin characters with black hair and you'll understand what I mean.
As for characters with white/silver/very faint colored hair, check if the character appears 90% with white/silver hair to buy a wig of that color. Break, from Pandora Hearts, actually has white/silver hair with lavender tones to it, so a white wig might not look good on him... but it may look good in someone that cosplays Squallo from Reborn. Unlike with black hair, the characters with very light colored hair usually only truly have white/silver hair when the shadow of said color is colored with grey tones, with sometimes some occasional color due to ambience light (sun, reflected light, etc). If the shading color varies too much it probably means the character's hair is indeed white or silver because it's reflecting the ambience light. Other characters, like Break, or Kuja, have light colored hair, not white, because 90% of the time the shadows of their hair are lavender-colored. Same applies for Ivan from Hetalia, his hair is not white like Prussia's, because it's always colored with a hint of dirty blond.
I hope this text helps anyone.
First, if you are using colored illustrations made by the mangá artist. Most commom media used for mangá colored illustrations are copic markers and watercolor. Both of them work with "soft colors", meaning even dark colors like dark brown hair or dark blue outfits may be colored very lightly, depending on the artist's style. A good way to check this is checking Hiromu Arakawa's work in acrylics and her works in copic markers, you can sense the density of the color of the acrylics is much heavier than in works made with copic markers.
Hence, you should be careful to not end choosing a color TOO LIGHT. But how you should know the right color? Well, you need to have a bit of common sense of what "looks natural". It's not because the artist used a FUCKING BRIGHT YELLOW that you should buy that ugly neon yellow wig, buy a blond one! Also remember that to create the illusion of profundity we use different shades and tones for the same color. Pick the intermediate color between the lightest and the darkest shade of the hair you see in the reference illustration you've chosen and you'll probably get what is the actual color of the character's hair. But remember, use your common sense always, this does not work 100% of the time.
Another tip particular for characters with dark hair is that they usually have lighter hair in watercolor/copic marker illustrations than what their hair should look like in real life. If you KNOW the character has very dark hair but the mangá shows a pic of him with... well, brown/blue/purple/green hair you should consider twice before using light brown/blue/purple/green: does it look natural on you? Does it make you look like the character indeed?
Now for those who use acrylics/cel shaded (anime)/pastel illustrations for reference: Some characters that have BLACK HAIR sometimes appear with colored highlights. THAT DOESN'T MEAN THE CHARACTER HAS BLUE/GREEN/(insert color here) hair, it means he has black/very dark hair that when exposed to light will show a faint colorization inclined for said color. Check Rurouni Kenshin characters with black hair and you'll understand what I mean.
As for characters with white/silver/very faint colored hair, check if the character appears 90% with white/silver hair to buy a wig of that color. Break, from Pandora Hearts, actually has white/silver hair with lavender tones to it, so a white wig might not look good on him... but it may look good in someone that cosplays Squallo from Reborn. Unlike with black hair, the characters with very light colored hair usually only truly have white/silver hair when the shadow of said color is colored with grey tones, with sometimes some occasional color due to ambience light (sun, reflected light, etc). If the shading color varies too much it probably means the character's hair is indeed white or silver because it's reflecting the ambience light. Other characters, like Break, or Kuja, have light colored hair, not white, because 90% of the time the shadows of their hair are lavender-colored. Same applies for Ivan from Hetalia, his hair is not white like Prussia's, because it's always colored with a hint of dirty blond.
I hope this text helps anyone.