Royal enthusiasts believe they've noticed yet another alteration in Kate Middleton's appearance - yes, once more, and this time, it's sparked a conspiracy theory.

The Princess of Wales' hair has been a mystery captivating the internet for about a month now, ever since she initially transitioned from her brunette style to a lighter shade at the beginning of September.

However, the transformation was actually first observed in August, as she was photographed through a car window while en route to a church service in Scotland.

Then, a few weeks later, she publicly showcased the hairstyle for the first time during a visit to the new gardens at London's Natural History Museum on 4 September.

But confusion arose when just a few days later, Kate attended another royal event, and this time her hair appeared brown once more.

The internet is once again obsessed with Kate Middleton's hair (WPA Pool/Getty Images)

She and Prince William visited the National Federation of Women’s Institutes on 8 September to mark the third anniversary of Queen Elizabeth II's passing.

And some of the photographs taken seemed to show the Princess's hair appearing dark again, leading some to believe she had reverted to her previous hair color. However, it soon became apparent that it was likely a play of lighting and angles that made it appear so different, as it looked blonde again in other photos.

Then, to add to the confusion, a photo of Kate at the Duchess of Kent's funeral at Westminster Cathedral on 16 September had been edited to make it seem like her hair was silver and her outfit was blue, when it was actually black.

One Twitter user wrote: Am I suddenly colorblind? She was wearing black from head to toe, and her hair wasn't grey either... What's the point of that?"

While a second added: "I don’t know who is tampering with filters, lighting & contrast, but the Princess of Wales was wearing her black bow tie Catherine Walker coat dress & certainly not a navy blue version."

And now, the saga continues.

The Princess of Wales first debuted blonde locks earlier this month (Max Mumby/Indigo)

More photos of the Princess of Wales have reignited the internet's fascination with her hair - this time with pictures taken at a school in Southport on Tuesday (23 September).

The visit was to view a new playground built to honor the young girls who tragically lost their lives at a dance class in the town last year.

On Reddit, one user shared a photo of Kate's hair appearing darker once again, and quipped: "Kate - from brunette, to blonde (ish) now back to a darker shade."

Another royal fan bluntly commented: "This is getting out of hand".

Some fans even speculate that the frequent changes in color could mean Kate is experimenting with different wigs, rather than dyeing her natural hair each time.

Someone wrote: "That would be so damaging for her hair! No way they could keep dyeing it that often and have it remain healthy. It has to be wigs," while others added: "At this point I think she’s just wearing different wigs every day" and "Definitely a wig".

Kate's latest 'hair change' has sparked a conspiracy theory (WPA Pool/Getty Images)

Meanwhile, others rightly pointed out that if it is a wig, who cares?

"What does it matter? People are allowed to try new things, even when they're ill-advised. I can't tell you how many times I've gotten curtain bangs thinking 'this time I'm going to rock' only to regret it the very next day," one person commented.

They added: "If I had her money, I'd probably have wigs of every different shape, size, and color."

While another agreed: "So what? She's experimenting with her look. Something every woman is entitled to do."

They added that Kate 'experimenting with wigs to try out new looks' is 'probably the most normal thing' they've ever seen her do.

Who knows - it could even be a trick of the camera again... either way, hopefully this is the end of the Kate hair debate!