Random UI Theme Color Set Generator

Description

Generate a random accent for a supplied opaque background under explicit contrast policies, select black/white text roles by the imported luminance contrast calculation and return role checks; not a complete theme or accessibility certification.

An interface fixture makes content and state explicit so a consumer can test a rendering or interaction. Literal labels, modeled states, and calculated geometry remain separate from what a browser or assistive technology actually displays or announces.

When to use this tool

Use this generator to create reproducible ui theme color set cases from the supplied model or bank. Inspect the returned evidence before using cases in a test or exercise.

How to use the tool and how it works

Supply background, minimumTextContrast, minimumAccentContrast, maximumAttempts in the field shapes below. Set seed when you need an explicit replay.
Run the tool and correct any input error. For generated controls, distinguish a successful fixture containing an invalid case from failure to generate the fixture.
Read background, text, accent, onAccent, textBackgroundContrast, accentBackgroundContrast, onAccentContrast, attempts. Use the conventions below and keep answer-bearing fields separate when presenting an exercise.

Select whichever of black/white gives greater background text contrast, then draw accent colors until accent/background and black-or-white-on-accent satisfy the caller’s thresholds. Return chosen roles, delegated contrast ratios and attempts used.^[1]

Input field	Meaning and units	Accepted input
background	Background	Required. Text; minimum UTF-16 length 7; maximum UTF-16 length 7.
minimumTextContrast	Minimum Text Contrast	Required. Finite number; minimum 1; maximum 21.
minimumAccentContrast	Minimum Accent Contrast	Required. Finite number; minimum 1; maximum 21.
maximumAttempts	Maximum Attempts	Required. Safe integer; minimum 2; maximum 8192.
seed	Optional numeric seed; takes precedence over context randomness. Without either, use the fixed tool.io default seed.	Optional. Safe integer.

Output field	Interpretation	Returned shape
background	Background	Required. Text; minimum UTF-16 length 7; maximum UTF-16 length 7.
text	Text	Required. Text; minimum UTF-16 length 7; maximum UTF-16 length 7.
accent	Accent	Required. Text; minimum UTF-16 length 7; maximum UTF-16 length 7.
onAccent	On Accent	Required. Text; minimum UTF-16 length 7; maximum UTF-16 length 7.
textBackgroundContrast	Text Background Contrast	Required. Finite number; minimum 1; maximum 21.
accentBackgroundContrast	Accent Background Contrast	Required. Finite number; minimum 1; maximum 21.
onAccentContrast	On Accent Contrast	Required. Finite number; minimum 1; maximum 21.
attempts	Attempts	Required. Safe integer; minimum 1; maximum 8192.
randomness	Replay metadata: source is seed or context; seed is the normalized 32-bit seed or null for a context source.	Required. Object; no unknown keys.
randomness.seed	Optional numeric replay seed; normalization and precedence are explained below.	Required. Safe integer. or Null.
randomness.source	Source	Required. Text; one of "context", "seed".

An explicit safe-integer seed takes precedence over injected context randomness and is normalized to an unsigned 32-bit integer. With no seed and no context source, replay uses the fixed tool.io default seed. A context source must return finite values from zero inclusive to one exclusive; its advancing state must be retained separately. randomness records the source and normalized seed, or null for context. These generators are not cryptographic random sources.

json

{
  "input": {
    "background": "#FFFFFF",
    "minimumTextContrast": 4.5,
    "minimumAccentContrast": 3,
    "maximumAttempts": 256,
    "seed": 42
  },
  "output": {
    "background": "#FFFFFF",
    "text": "#000000",
    "accent": "#DA3B32",
    "onAccent": "#000000",
    "textBackgroundContrast": 21,
    "accentBackgroundContrast": 4.513480177756666,
    "onAccentContrast": 4.652728974748179,
    "attempts": 3,
    "randomness": {
      "seed": 42,
      "source": "seed"
    }
  }
}

Limitations and assumptions

Impossible text thresholds and exhausted accent attempts are errors. These checks do not constitute a complete theme, account for every UI state or certify accessibility.
A replay requires the same complete input and implementation. Randomized construction does not guarantee uniform coverage of every feasible output; finite samples can repeat unless a distinct-selection rule is explicitly stated.
The field tables state structural bounds; cross-field constraints and bounded search or output budgets also apply. Unknown keys are rejected where the object contract disallows them. Input errors are distinct from null fields and deliberate invalid controls in a successful output.

Alternative or Complementary methods

For a supplied example, inspect the returned construction or delegated check directly. To evaluate a consumer, also test cases chosen for its own boundaries; a generated finite corpus does not establish exhaustive coverage.

References

Tool behavior and example: Random UI Theme Color Set Generator — tool.io

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