Color Brightness

Overview

Color Brightness Calculator works by applying WCAG 2.0 relative luminance formulas to RGB color values, calculating contrast ratios with black and white, and determining optimal text colors for accessibility.

Live Test Color Brightness Source →

Formula

One function covers the whole catalog: the first argument names the source, the rest are its inputs, and the "field" pair says which single value lands in the cell. Formulas covers the grammar that applies to all of them.

=VERVE("colorbrightness", A2, "field", "is_light")

A2 holds the hex you are looking up. Drag the formula down and each row resolves on its own.

With literal values

Nothing has to come from a cell — typed values work the same way.

=VERVE("colorbrightness", "FF5733", "field", "is_light")

Inputs

Required inputs are positional, in the order below. Everything else is passed as a "name", value pair after them — the same shape as SUMIFS. Premium inputs are accepted on every plan but only take effect on plans that include them.

Input	Type	Where it goes	Description
`hex`Required	string	argument 2 (A2)	Hex color value (with or without # prefix) hexColor

What lands in your sheet

The "field" pair is what makes the formula resolve to one cell. Its value is a dot-path from the table below, so swapping it is how you pull a different value — one formula per column.

Seeing everything at once

Drop the "field" pair and the formula returns the whole response instead: two columns, field name on the left and value on the right, spilling from the cell you typed in.

=VERVE("colorbrightness", A2)

Good for exploring, not for filling down

The second row's table would land on top of the first's, and every cell after the first reads #REF! (#SPILL! in Excel). Keep one per sheet, or name a field, and leave the cells below and to the right empty.

Response fields

Paths are relative to data. Each one is exactly what the "field" pair accepts, so swapping it is how you pull a different value into a cell. On a plan without a Premium field the cell reads #PREMIUM(field) rather than a value, so a locked field never looks like a real answer.

Use as "field"	Type	Example cell value	Description
`hex`	string	`#FF5733`	Hexadecimal color value provided in the request
`rgb`	object	`{…}`	RGB color components: red, green, blue values
`rgb.r`	number	`255`	Red component value between 0 and 255
`rgb.g`	number	`87`	Green component value between 0 and 255
`rgb.b`	number	`51`	Blue component value between 0 and 255
`luminance`Premium	number	`0.2832`	Relative luminance calculated using WCAG 2.0 formula
`perceived_brightness`Premium	number	`131`	Perceived brightness score from 0 to 255
`yiq`Premium	number	`133.13`	YIQ color space brightness value for brightness analysis
`is_light`	boolean	`false`	Boolean indicating if color is considered light
`is_dark`	boolean	`true`	Boolean indicating if color is considered dark
`brightness_category`	string	`dark`	Brightness classification: light, medium, or dark category
`recommended_text_color`Premium	string	`#FFFFFF`	Recommended text color for optimal contrast and readability
`contrast_ratio_with_white`Premium	number	`3.15`	WCAG contrast ratio calculation between color and white
`contrast_ratio_with_black`Premium	number	`6.66`	WCAG contrast ratio calculation between color and black
`wcag_aa_compliant_with_white`Premium	boolean	`false`	Whether color meets WCAG AA contrast requirements with white
`wcag_aa_compliant_with_black`Premium	boolean	`true`	Whether color meets WCAG AA contrast requirements with black
`wcag_aaa_compliant_with_white`Premium	boolean	`false`	Whether color meets WCAG AAA contrast requirements with white
`wcag_aaa_compliant_with_black`Premium	boolean	`false`	Whether color meets WCAG AAA contrast requirements with black

Filling a whole column

Both platforms make one batched call for a column rather than one request per cell, and both cost the same — 2 credits per row looked up. How you write it differs, because the two runtimes batch at different points.

Rows 2–100 in one call

=VERVE("colorbrightness", A2:A100, "field", "is_light")

In Google Sheets, give the arguments ranges and the answers spill down from the cell you typed in. Custom functions there run synchronously and in isolation, so dragged cells cannot be coalesced — the range form is how a column becomes one call. The "field" pair is required here: a per-row two-column table has nowhere to spill. Use a full column per input (A2:A100, not A2) — a single-cell reference is read as row 1 only and the rest of the column comes back blank.

In Excel, type the formula once and fill down — no range form and none needed, because its runtime is asynchronous and the add-in coalesces the calls a fill produces into a single batched request. Do not hand VERVE.CALL a range: Excel flattens it into positional arguments, so A2:A100 arrives as a hundred separate arguments and the cell reads #ERR rather than filling.

Either way, column A holds your hex values and the answers land beside them, one row each, blank rows skipped.

When a cell doesn't fill

A failed lookup returns readable text starting with #ERR rather than a spreadsheet error, because Excel cannot show a custom message on a real error — you would get a bare #VALUE! with no reason. The trade-off is that IFERROR() will not catch it; test with LEFT(cell, 4) = "#ERR" instead. Error handling covers the rest.

Cell reads	What happened
`#ERR Not connected`	No API key saved. Open the side panel and connect your account.
`#ERR Replace <name> with a cell or value`	A preview formula was copied as-is. Swap the placeholder for a cell reference.
`#ERR No "x" in colorbrightness`	An option name this source does not take. The message lists the ones it does.
`#ERR No data point "…"`	The `"field"` path is not in the response. Check it against the table above.
`#PREMIUM(field)`	The field exists but your plan does not include it.
`#ERR Out of credits`	The cycle's credits are spent. Usage resets on your billing date.

Before the formula works

The add-in reads the API key you saved once in the side panel — the key never goes in the formula, so a shared sheet does not leak it and a collaborator without access simply sees the last calculated values.

Install the add-in for Google Sheets or Excel.
Open the side panel and sign in, or paste a key from your dashboard.
Type the formula above into any cell.

Use cases

Web Accessibility: Ensure WCAG compliance by calculating contrast ratios for text and background colors
UI Design: Determine appropriate text colors for backgrounds based on brightness calculations
Theme Development: Automatically select light or dark text based on background color brightness
Color Analysis: Analyze color brightness and categorize colors for design systems and palettes

Other ways to use Color Brightness

Set up Color Brightness on VerveSheets, or reach the same source a different way. Your VerveSheets account and credits work on all of them — one key, one balance.

Call it as a REST APIOne HTTPS endpoint and an x-api-key header, with SDKs for Node, Python and .NET.APIVerve →Reference →

Give it to an AI agentConnect over MCP and your agent calls it as a native tool — Claude, Cursor, ChatGPT.VerveKit →Reference →

Ground an agent on itA cited, machine-checkable fact your model can't produce on its own.VerveContext →Reference →