Color Calibration of two Dell U2415 monitors - both too yellow?

I just received two Dell UltraSharp 24 U2415 monitors, which proudly boast "Award wiing monitor with unbeatable color".

I am hooking these two up to a single laptop, an ASUS GL551K ruing Windows 10. One of them is via the provided Mini DisplayPort cable, the other through an HDMI cable to HDMI input on the monitor.

The problem is they both look bad. The whites are yellow, and as someone who stares at a sea of code all day, none of the colors look familiar.

They look fine on the laptop, nice bright whites, but both of the Dells are no good. I hooked it up to a Mac and it looks a lot better on that side.

To make a long story short, I have tried all of the following, and am unable to get a pure "white" color on either of these two monitors:

• Use in-monitor menu system to reset every option back to "factory defaults"
• Went into Color Calibration in Windows 10 and remove any pre-set profiles there, whether my own or Dell's
  • Ran monitor calibration, and it looks fine for gamma, contrast, and gray
  • Manually adjusted the RGB sliders to attempt to get a whiter white, but as close as I can get, it is not white. It looks like faded paper.

I highly doubt that I could get delivered two top-selling 24" monitors and both of them have a problem, so I'd just like to know how to adjust this. I went through other tutorials step-by-step, and so far, no luck.

Thanks!