Take your mayo, mix 50-50 with ketchup.
Or do 2/3 and 1/3 or 1/3 and 2/3.
Enjoy. ;)
You can also do 3/4 mayo and 1/4 mustard.
Myself, I love to dip tater tots in mustard.
Since we are exchanging recipes, try Horseradish, Mustard, and Mayo. Equal parts or however you like it. Fantastic on ham sandwiches, never tried it on fries.
A flavor profile I really love is the addition of mustard into cheese sauce. Example: If you cooked one pound of elbows and make cheese sauce for it, add one or two tablespoons of brown mustard like Guldens.