New Apple signs put up at its retail locations say the company’s long lost white iPhone 4 will be “available spring 2011.”

[ad#Google Adsense 300×250 in story]On the surface, that’s not new. Apple previously said that the device had been delayed until spring, but this is the first time I believe that Apple has begun advertising the white iPhone again.

As TUAW points out, finding the white iPhone is kind of like finding a unicorn (nice graphic guys), but some people have held off on purchasing an iPhone until they can get the white model.

Apple has never given a reason for the delay of the white iPhone 4, other than it has “proven more challenging to manufacture than expected.” Originally scheduled to be released shortly after the black iPhone, the white iPhone 4 delayed in late July until “later this year,” and again in October until spring 2011.