Either the shoot is from the rootstock below the graft and it is the variety 'Dr. Huey' used for that purpose, or it is mutation (sport). Sometimes sports are stable and other blooms on that cane will be red. Color sports are fairly common on roses.

Say hello to 'Dr. Huey'. This rootstock variety is widely used in the industry and commonly sends up unwanted suckers from below the graft union, eventually choking out the desired scion variety. Once sucking starts, its usually an uphill battle to stop it for the remainder of that rose's life.

I won't grow roses budded to this horrible rootstock. It is used for the convenience of the industry, not for the benefit of the end consumer.

Find the source/base of the cane with the red rose. If the source is below what is called the bud union (see the photo at the link below), then that is what we call a "sucker" from the rootstock. Go down to the base and scrape off that sucker from where it is attached to the rootstock. Dr. Huey is vigorous, and only by scraping it off at the base will help you save your white rose. Don't cut it, that won't help.

If the source is above, then it is a sport. Methinks, though, that it is a Dr. Huey sucker.

Here is a link that might be useful: Anatomy of a Bare Root Rose

Do the red flowers look like this?

Say hello to Dr. Huey.

Wow you guys are good, the red rose looks just like your pic.

You probably purchased at the Schillinger & Airport Blvd store right? They are notorious for that I hear.

Many of us have met the Dr.... :-P

I had a Tradescant years ago that produced maybe a handful of actual Tradescant blooms in 3 years.
I spent a lot of time removing one sucker after another, and finally dumped it.
Some roses just never got all the Huey bud eyes removed.

Jeri