They will be cute for sure but you can't sex by the color. You'll have to wait until they loose their little peeps and either quack or rasp like a frog.
Yellow feathers predominantly become white feathers when they get their adult feathers. Runners come in a lot of color varieties so color will not help with sexing at all.
@Miss Lydia might have a better guess to color variety you ended up with.
I have two adult drakes that are fawn and white so these will fit right in
I’m begging God that they are females please please please!! The small one Is a loud mouth already so I’m pretty sure she’s a girl ( Susan) but the middle one with the odd eye shape and darker head ( daisy) isn’t loud and is scaring me some