Do you remember when the Project Red came out for the 7? How long did Apple release the red when the 7 was first released?It's Possible Apple could release a refreshed iPhone X color during a spring Keynote if they do hold one or they could have a silent update it without a key note with a new color, but otherwise it will likely be next fall 2018 when they expand the iPhone X color lineup.
The phone just came out, and the color is only on the back - slap a case on the bad boy and you can have any color that you wish
Shocked? I mean come on most people put cases on their phones anyways.
The color choice is almost irrelevant for most people, but there were some rumors I believe of new colors in March of next year, along with an updated SE. So maybe then.
Which, IIRC, just sort of magically appeared, not connected to any special event.