Last updated 3 September 2026
Reading a hex code without a picker
A hex colour is three pairs of digits — red, green and blue, each from 00 to FF. Once that clicks, a code stops being a random string and starts being readable: a high first pair with low others is a red, high red and green with low blue is a yellow, and three roughly equal pairs is a grey whose lightness you can read straight off the value. The trap this game sets is that the decoy swatches differ only slightly, so recognising the family is not enough — you have to judge how far along it the value sits. That is a genuinely useful skill when reading someone else's stylesheet, and it gets sharper with a surprisingly small amount of practice.
Related guide: How to build a brand colour palette that works
Why colour matching by eye is hard
Human colour perception is relative, not absolute. The same hex value looks different depending on what surrounds it — a mid grey appears lighter against black and darker against white, which is simultaneous contrast and it operates whether you know about it or not. This is why matching a colour against a changing background is genuinely difficult rather than just fiddly.
Sensitivity also varies by channel. The eye distinguishes far more steps in green than in blue, so a shift of ten in the green channel is obvious while the same shift in blue is often invisible. That is a direct consequence of the retina having roughly twice as many green-sensitive cones as red-sensitive ones and comparatively few blue.
Reading a hex value
Each pair of characters is one channel, from 00 to FF, so #3A7BD5 is red 58, green 123, blue 213. A few patterns make values readable at a glance: when all three pairs are equal the colour is a neutral grey, and the higher the value the lighter it is. Raising all three pairs by the same amount lightens without changing hue. And the pair with the largest value tells you which primary dominates, which is usually enough to guess the family before you see it.
One caveat for anyone matching colours for real work rather than practice: what you see depends on your display. An uncalibrated monitor, a colour profile mismatch, and phone screens with saturation boosting all shift the appearance of the same value. For anything that has to match across devices or go to print, judge by the numbers rather than by eye.
Common questions
How do I read a hex code?
It is three pairs: red, green, blue, each from 00 to FF. #FF0000 is pure red, #00FF00 pure green, #0000FF pure blue. Equal pairs make grey, and how high they are tells you how light that grey is.
Does it get harder as I go?
Yes. The decoy colours start noticeably different and move closer to the correct answer as your score rises, so later rounds require real discrimination rather than recognising the general family.
Is there a trick to getting better?
Read the first pair as how much red, the second as how much green, the third as how much blue, and compare pairs against each other rather than reading the code as a whole. Judging which pair is largest gets you the family; judging the gaps between them gets you the shade.
Is my score saved?
Your best score is stored in your own browser. Nothing is uploaded and there is no account.
Why does the same colour look different against different backgrounds?
Human colour perception is relative. A mid grey looks lighter against black and darker against white — an effect called simultaneous contrast. The pixel values have not changed, only what surrounds them, and the effect operates regardless of whether you are aware of it.
Do I need to convert hex to decimal to compare two colours?
Not usually. Each pair runs from 00 to FF, which is 0 to 255 in decimal, but the ordering is the same either way, so you can compare pairs directly in hex. Converting only helps when you need the exact numeric gap — when checking a contrast ratio, for example.
Why do some channel changes seem invisible?
The eye is far more sensitive to green than to blue, because the retina has many more green-sensitive cones than blue-sensitive ones. A shift of ten in the green channel is usually obvious, while the same shift in blue often is not.