Hair Color Changer: Try On Hair Color on Your Photo

Every hair color chart starts with the level, the lightness of the hair from 1, black, to 10, the lightest blonde. The tone comes second: natural, ash (cool), gold, copper, red or violet. The try-on’s swatches are laid out the same way, ten levels by six tones, so a swatch is a level and a tone you can ask a colorist for.

The third column is the lightness (L*, 0 black to 100 white) of each level’s hair as a camera records it, measured on 342 reference photos with levels called by eye, fitted so each level is lighter than the one before. It is what the changer reads your photo against, and the lightness each swatch takes your hair to. The last two columns are what lifting hair to that level shows and the toner that cancels it.

The level names follow the cosmetology board charts; brands word levels 2 and 10 slightly differently. Charts also differ by about a level on the pigment column, so read it as a band: red up to level 4, orange around 5 and 6, gold around 7 and 8, pale yellow at 9 and 10.

The changer takes the median lightness of the pixels it is sure are hair and places it between the levels in the chart above, halfway between neighbors. It shows the level with one either side, Level 6 (5 to 7), because that is the honest precision of a photo: on 342 reference photos the shown range held the level called by eye 80% of the time, and the four bands of the chart (1 to 3, 4 and 5, 6 and 7, 8 to 10) matched 74% of the time. Of 207 photos called black to dark brown, 169 read levels 1 to 3, so those levels read as one.

The same photo read again came back on the same level 80% of the time across 3,624 versions (a little darker and brighter, recompressed, half size, mirrored and cropped). Exposure moves it most: a photo 15% darker read 3.1 L* darker at the median and kept its level 46% of the time, 15% brighter 2.6 lighter and 58%. Shoot in even daylight, facing the light, for the truest level.

It reads the lightness of what the photo shows, so dyed hair reads its dyed level and gray or white hair reads as a light level: the level scale describes pigment, and the changer cannot tell gray from blonde. Highlights and roots average into one level. It is a cosmetic reading, not a colorist’s consultation.

Lightening breaks down the dark pigment in hair first, and the warm pigment underneath shows: red at the darker levels, then orange, gold and pale yellow as the hair gets lighter. That warmth is the brass. A toner cancels it with the color opposite it on the color wheel: green cancels red, blue cancels orange, violet cancels yellow (Behind the Chair’s color wheel reference card).

When you tap a lighter shade, the result names the warmth that level shows and its toner. Gold, copper and red shades keep part of that warmth on purpose; ash and natural shades cancel it. Purple shampoo is a violet toner for pale yellow, which is why it suits pale blonde, while orange brass needs blue.

The result compares the shade with the level your hair reads now and puts the change in one of four groups. Darker: color is deposited, not lifted, and the American Academy of Dermatology says dyeing darker is typically better for hair than lighter. About your level: only the tone changes, which a demi-permanent color or a gloss can deposit. Up to 3 levels lighter: within the 3 shades of your natural color the AAD suggests staying inside. More than 3 lighter: past that line, where the AAD notes stronger peroxide and more damage.

For lifts the result also names the developer: 20 volume developer lifts 1 to 2 levels; 30 volume developer lifts 2 to 3 levels; 40 volume developer lifts 3 to 4 levels, and is used off the scalp only (Behind the Chair’s card). Past 4 levels, colorists lighten with bleach first and tone after. Fashion shades such as pink, lavender and silver are usually lighter than the hair underneath: a dye that only deposits color cannot make hair lighter, so the result says how far your hair has to be lifted first.

Whatever you choose, test store-bought color before you use it, as the box says. A rash, redness, swelling, burning or itching is an allergic reaction to the dye (AAD): stop, and a dermatologist can test you for it.

The try-on shows a color on you; it does not judge whether it suits you. For shades picked for your skin, the hair color for skin tone matcher takes your depth and undertone and suggests four hair color families, and its result opens them here as swatches on your photo. The color season analysis reads your skin, hair and eyes for a 12-season palette, and the undertone test reads warm, cool, neutral or olive from a photo.

The before and after divider puts your skin next to both colors in the same light, and tapping the tones on one level shows how ash, gold, copper, red and violet change the same lightness. For the cut to go with the color, the hairstyle finder matches cuts to your face shape.

The changer works on any photo with your hair in it. These make the matte cleanest and the level reading truest.

Checked by eye on 48 reference photos picked at random, the matte covered the hair cleanly on 43, missed or spilled a little on 4 (the ends of long hair, a microphone in front), and spilled onto a background close to the hair’s color on 1. Recolored to each level’s natural swatch and read again, 95% of 6,100 recolors read the swatch’s own level and all were within one, so the swatches land where the chart says.

On a laptop an 800 by 1000 photo is ready in about 0.4 seconds and each shade takes about 3 ms; with the processor slowed 4 times, a stand-in for a phone, about 1.7 seconds and 11 ms. The model is fetched once, 16.4 MB, with the share loaded shown on screen.

It colors all of the hair the photo shows at once, so balayage, highlights and roots are not drawn as separate pieces. Beards and eyebrows keep their color, because the segmenter counts them as face. Very dark hair in a dim photo has little texture to keep, so light shades look flatter on it; a brighter photo shows more strands. And a real dye result depends on your starting level, any color already in your hair and how porous it is, none of which a photo can see.