Not Blue Enough!
If your company has a uniform policy, it’s up to the company to provide uniforms to the employees. Or, at the very least, give them clear instructions on what the dress code is. Don’t just tell your employees they should wear “blue” since there are over a million shades of blue.
And that was the reason they were fired. After being told to wear blue, the OP purchased a blue shirt, which wasn’t the correct shade of blue. And the worst part was that the employer didn’t even provide clear details of what kind of blue they wanted!