branding - Is company permission necessary for changing the color of a logo?

I am designing a series of landing pages for a company I work. There are a number of other company's logos included and the design would look much better if the logos were grayed out. From looking at each company's brand guidelines, I see that most allow for this apart from a few, but my managers insist that company permission is necessary for this.

Is this true?

If not, what's the best way to argue for this?

i.e. the argument that this is a fairly common practice doesn't seem to stick