I'm building a site that aggregates food delivery services in my region. I show all the companies I collected as a list of cards, where each card contains the logo of a company, company name, link to the site of the company and other information.
I have one problem though. Some companies use white logos on a transparent background. My site's background is white, therefore those logos are invisible. Is it legal to invert the logos (make them black) without asking each company?
I take it that you intend using the logos of the various companies to show that you do business with them? That would be "nominative use" and would be legal even without permission, but it would be better practice to ask for permission. You would need to make it clear that these companies do not endorse or recommend you (unless they do and say so in writing).
If you get permission, ask about any color variations they are OK with. Would it be possible to put a black or dark color undercard below any logos that are white on transparent? this would make them visible and be a minimal change to the standard form of the logo. Again, the key thing is to make it clear that you are not claiming to be any of those companies, nor to be endorsed by them.
And yes, a short consultation with a lawyer knowledgeable in trademark law would be a very good idea, and might not be very expensive.
Most large companies are touchy about use of their logos.
Even when they give permission, virtually all of them have logo and style guidelines that they want you to follow. Those guidelines will tell you how to deal with a reverse background.
Further, I gather you are not building this aggregator for free, and you have affiliate deals with some or all of the companies. This is a complex legal contract which you may have clicked past in the blink of an eye, and you may want to take the time to skim it for what it says about brand and logo usage.
The law here? The law (practical) is that if they don't like what you are doing, they hit you with a Cease & Desist, and you stop. Or they threaten to cut off your affiliate payments and you say "yessir!"
The law (actual), if you would rather die on that hill than run your business, is that yeah, you have a limited right to use their names, and possibly their brands and logos, referentially. However, against a well-capitalized granfalloon, the law is less about who's right than who has the stamina for extended litigation. You will get squished unless you're willing to spend 8 hours a day learning to be an amateur lawyer, in which case you can be a tremendous nuisance as a pro-se litigant, at the cost of free time, business, job, spouse, family, etc.
