HEX Color Codes Explained: What They Are and How to Use Them

Published 2026-08-17 by Image Color Changer

HEX color codes appear everywhere in web design, CSS, design tools, and image editors. They look technical at first, but they are just a compact way to write RGB colors. Once you can read and write them, tasks like choosing target colors, matching brand palettes, and entering values into a color replacement tool become much easier.

This guide explains what HEX codes mean, how they work, and how to use them when editing images.

The Structure of a HEX Code

A HEX code has six characters after a hash sign: #RRGGBB. The six characters are three pairs:

• The first two set the red channel.
• The middle two set the green channel.
• The last two set the blue channel.

Each pair is a hexadecimal number from 00 to FF. In decimal terms, that is 0 to 255. 00 means the channel is fully off; FF means it is fully on.

A few examples make this concrete:

• #FF0000 is pure red: red on, green off, blue off.
• #00FF00 is pure green.
• #0000FF is pure blue.
• #FFFFFF is white: every channel fully on.
• #000000 is black: every channel fully off.
• #808080 is mid-gray: every channel at half.

Why Hexadecimal?

Hexadecimal is base 16: it counts 0-9 and then A-F. Two hex characters cover 256 values, which is exactly the range of one RGB channel. That is why each pair in a HEX code uses two characters, and why the code is exactly six characters long.

Writing #FF8800 is shorter than writing "red 255, green 136, blue 0", and it is accepted by nearly every tool. That convenience is the main reason the format stuck.

Reading a Code Without a Tool

You can estimate what a HEX code looks like without converting it:

• Higher values in a channel mean more of that color.
• Equal values in all three channels produce a shade of gray.
• A code with red and green high and blue low, like #CCCC00, looks yellow.
• A code with red and blue high and green low, like #CC00CC, looks purple or magenta.

For precise work, use a color picker to see and sample exact values. If you need to pull a code out of an image, read how to find a HEX color code.

Using HEX Codes in Image Color Replacement

In the image color editor, both the source color and the target color are entered as HEX references. The workflow is:

1. Sample or write the HEX code of the color you want to replace.
2. Enter it as the source color.
3. Enter the HEX code of the new color as the target.
4. Adjust tolerance and apply the change.
5. Inspect the preview and download the result as PNG.

Note that the target HEX is a reference, not a guaranteed output. The editor changes hue while keeping the source image's saturation and lightness variation, so highlights and shadows stay realistic. Exact, flat output requires a vector or layered editor. For a full explanation, see color theory for image editing.

Common Notation Mistakes

Small typos break color workflows. Watch for these:

• Forgetting the leading hash sign.
• Using only three characters when the tool expects six. Shorthand like #F00 works in CSS but not in every editor.
• Confusing letters and numbers: 0 versus O, or 1 versus l.
• Mixing up pairs: #15EB84 and #158EB4 are different colors.
• Copying a code with extra spaces or invisible characters.

When a replacement does nothing or produces an unexpected result, check the entered values first.

Build a Small Working Palette

A practical way to build comfort with HEX codes is to keep a small palette of codes you use often. Store your brand colors, your dark mode shades, and a few neutral grays in a note, and copy from that list instead of re-typing.

That small habit removes most entry errors and makes every edit faster, whether you are changing a background color, recoloring a logo, or testing product variants. If you are ready to apply one, start with how to change the color of an image.