Lo and behold,
the yellow Nexus 5 is real. Despite not yet being available on the Play Store, Google’s fifth Nexus is set to receive a fourth colour variation after debuting with black and white and, later, adding a stunning red variant.
Captured in what appears to be a banner image set to go live shortly, the yellow Nexus 5 shows up alongside another unannounced device, the Samsung Galaxy S5 Google Play Edition, or GPe, usually reserved for then US market. It’s also interesting to note that the Galaxy S5 is the first Samsung flagship to use on-screen buttons, even while retaining a hardware home button. This may be a rendering error, but if it pans out it will make the home button, at least on this version, quite redundant.
It’s unclear when the yellow Nexus 5 may be added to the aging smartphone’s lineup, but it shouldn’t be too long of a wait now.
Update: Looks like the yellow Nexus 5 is, as stated in the comments, a regular one in a yellow bumper.