How to use hex color code in v3 after upgrade from v2 to v3

I have used tailwind css colors like bg-primary-500 in v2 and after upgrade to v3 I want to use hex color code like #fffff but when i am taking any hex code from documentation and giving a custom name like 'test' => Color::hex(#ff0000) it is not showing the output in UI but if I give 'primary' => Color::hex(#ff0000) it is showing in UI. How can I fix this? Thank you