I'm currently working a client who had their brand colors set before I started with them. Their primary color is red with a supporting blue and some grays. My question is for errors on the page would it be bad to use their red? I'm worried that psychologically their users will begin to associate that red with negative events, thus creating a negative connotation when they see it. Thoughts?
What about the ol' red text on a light red (pink?) status banner thing pattern?
Even if you use the brand red for the text, the light red would differentiate it - yeah?
Though, I don't know the context of the problem you're trying to solve, so I'm unsure if this is a solution.
Have you considered making errors more neutral and friendly, anyways? Do we really need them to feel like OH FUCK SOMETHING IS WROOOOOOOOOOOOONG
You might consider going with a contrasting colour - maybe a green/cyan.
People are good with context though. They will make the differentiation between the colour of the brand and the error message as the error message is a reaction to a certain circumstance. And in most cases you can offset the negative effects of an error using nice copy - "oops, don't think that's your password". It's an opportunity to turn a bad experience into a good one.
I'd suggest using red very sparingly throughout the UI. If it's branding colors, try isolating it to branding only, not other elements. Then the error will have enough contrast. Psychologically, I don't think it's a big deal otherwise.