Fat help: I just opened a beef roast and there was a bright blueish purple on some of the fat. - Help.com

Doesn’t sound safe or appealing to me..

It was marked w ink?

Probably part of a mark of the slaughterhouse.

When you say bright blue-ish purple, do you mean it was like food coloring? Or are you talking about a shimmery reflective shining stuff?

If it’s dark, and stained, like a paint or dye, then you don’t want to eat it. But if it’s a shimmering, almost sparkly substance, then it’s something called Diffraction Grating, and it’s not anything to worry about. If it’s diffraction grating, it just means your meat is really juicy, and the water in the meat is refracting the light like a prism.

“New” for a roast beef isn’t good anyway, it must be “seasoned”.
And she said: “it wasn’t expired”.