hex color beginning with a 4 is not valid

[reedcodes]

I've been having an issue when attempting to build my color palette. I'm using hex color codes in my tokens.js file, and when I try to build, I get the following:

Error: Foreground and Background must be a valid CSS colour

It took me a while of adding and removing lines in my tokens.js and my package scripts to realize that the issue was when one of the colors' hex codes began with a 4. I tried several different formats of the same color, e.g. hsla or rgb works fine. It's only when the color code begins with 4.

Steps to reproduce, once the package is installed:

1. create a tokens.js file under ./source/_scss/colors
2. add a name/color pair where the color code begins with a 4, e.g. #40ffff
3. run npx a11y-color-tokens --outputDirPath='./source/_scss/colors --colorTokensPath='./source/_scss/colors/tokens.js'

My tokens.js file is like this:

module.exports = [
  {
    name: 'blue',
    color: '#40ffff'
  }
];