[colorManipulator] Theme colors in the new syntax without comma (rgb(106 27 154)) fail to generate correct contrast color for buttons

[kgrhartlage]

Steps to reproduce

Link to live example: codesandbox

Steps:

1. Assign a dark theme color in the newer syntax using the rgb color function, for example rgb(106 27 154)
2. Render a contained button that uses this theme color as its background: <Button variant="contained">click me</Button>
3. Observe the text color being dark as well
4. Change the theme color to the legacy syntax with commas: rgb(106, 27, 154)
5. Observe the button now having a white contrast text color

Current behavior

A dark rgb theme color in the new color syntax results in the wrong contrast text being applied:

I reckon this might affect other areas as well, but I have only identified this behavior for the Button component

Expected behavior

I expect a button with a dark theme color background to have white contrast text:

Context

No response

Your environment

Chrome Version 127.0.6533.120 (Official Build) (arm64)

npx @mui/envinfo

  System:
    OS: macOS 12.4
  Binaries:
    Node: 18.13.0 - ~/.nvm/versions/node/v18.13.0/bin/node
    npm: 8.19.3 - ~/.nvm/versions/node/v18.13.0/bin/npm
    pnpm: Not Found
  Browsers:
    Chrome: 127.0.6533.120
    Edge: Not Found
    Safari: 15.5
  npmPackages:
    @emotion/react:  11.13.0
    @emotion/styled:  11.13.0
    @mui/base:  5.0.0-beta.40
    @mui/core-downloads-tracker:  5.16.6
    @mui/icons-material:  5.16.6
    @mui/lab:  5.0.0-alpha.173
    @mui/material:  5.16.6
    @mui/private-theming:  5.16.6
    @mui/styled-engine:  5.16.6
    @mui/system:  5.16.6
    @mui/types:  7.2.15
    @mui/utils:  5.16.6
    @mui/x-date-pickers:  7.12.0
    @types/react:  18.3.3
    react:  18.3.1
    react-dom:  18.3.1
    styled-components:  6.1.12
    typescript: ^5.5.4 => 5.5.4

Search keywords: contrast, comma, rgb

[oliviertassinari]

It's the same thing as https://lea.verou.me/blog/2024/contrast-color/#does-this-mythical-l-threshold-actually-exist%3F no? actual color contrast is not the same thing as WAI-ARIA color contrast compliance. https://webaim.org/resources/contrastchecker/?fcolor=6A1B9A&bcolor=FFFFFF

Ah no, it's: related to #20492

[siriwatknp]

Let me check if #43289 fixes this issue or not.