Following his loss to Roman Reigns at WrestleMania 33, all signs had pointed to a retirement for The Undertaker. After Reigns pinned him, 'Taker received a huge ovation from the crowd, left his attire in the ring and embraced his wife Michelle McCool at ringside. He hasn't been seen or heard of on WWE programming since.

However, Harry Kettle of WrestleZone made an eye-catching observation -- a hint that maybe Undertaker is set for a return. Take a look at this photo Ric Flair posted of him with The Deadman:

Notice the colour of Undertaker's hair?

As Kettle pointed out, The Phenom usually leaves his hair grey when he's not planned to appear on WWE programming any time soon. He changes his hair and beard colours to black when he's appearing on television, so could this be the sign of a potential return?

It could very well just be a coincidence, like Kettle noted. But with the Survivor Series pay-per-view coming up, perhaps the creative team (and Undertaker), have decided that it's a good time for him to return.

Right now, it's impossible to know what the future holds for Undertaker. He is 52 years of age and required hip replacement surgery after WrestleMania. Given his age and the state of his body, it wouldn't be surprising if Undertaker decides to never wrestle again.

But 'Taker also didn't formally announce his retirement on television, something many legends like Ric Flair and Shawn Michaels have done in the past. Then again, Undertaker has seemingly given hints that he'd prefer a low-key and quiet retirement.

As mentioned above, Undertaker has always been one to return when we least expect it. For all we know, he could have several more matches in him. But then what would the purpose be of dying the hair black?

Perhaps we'll get a rare answer from him soon.