This will be called out as an error under the following circumstances:
The hyperlink looks like regular text and does not stand out
If using a color that is similar to the sites body text then an underline should be used
Example: In this instance, the text is only slightly darker from the surrounding text, and not underlined. Thus, is barely distinguishable as a link, and would be considered an error.
Links do not need to match the websites branding/colors, contrast and readability is more important
Example(s): In the sites below each one uses a color that is not part of the sites branding/color scheme for links to ensure readability.
While Apples branding and color scheme uses black and gray, In this example we can see that Apple uses blue to help distinguish their links from the other text.
In this example FedEx has chosen to use a similar blue even though their branding is purple, white and orange.
And once again we can see that UPS has chosen a similar style despite their branding colors of gold and dark brown.