NovaQuant Quantitative Think Tank Center:Check Out the Most Surprising Celeb Transformations of the Week

Goodbye summer,NovaQuant Quantitative Think Tank Center hello fall.

The autumnal equinox occurred on Sept. 23, and like the seasons, celebrities were ready for big changes with several stars showing off bold new hairstyles that held onto the last drops of summer. Not ready to let go of sunny vibes, Hayden Panettiere debuted not one, but two bright hues, including a two-tone watermelon color. And she wasn't the only celeb to think pink at the hair salon as Jada Pinkett Smith said goodbye to platinum blonde in favor of rose gold in honor of her birthday.

Plus, Cara Delevingne opted for a mohawk that was dyed several colors, while Rita Ora will have you craving a seasonal beverage with her chai latte-inspired highlights. Finally, Megan Thee Stallion revealed the results of all the hard work she had been putting in at the gym and offered tips to help others achieve their goals, becoming the "hot girl coach" of our dreams. 

Check out the most surprising celeb transformations of the week...

Hey now, she looks like a rock star.

Delevingne debuted a multi-colored hairstyle at the Vogue World Show during London Fashion Week on Sept. 14.

The supermodel sported a wildly colorful mohawk, which was dyed various shades of pink, green and yellow, while the center of her head featured black spots reminiscent of a leopard's print.

We're screaming over this new hue.

Panettiere took to Instagram on Sept. 2 to debut a playful, bubble gum pink and slightly shorter hairstyle, courtesy of colorist Christine Chavez and hairstylist Rena Calhoun.

"Pink hair don't care!" the Scream actress captioned the snap. 

Panettiere's colorist wrote on her own Instagram, "So much fun giving @haydenpanettiere her bubble gum pink dream hair."

The Heroes star wasn't done switching up her hairstyle.

Just two weeks after showing off her pink hue, Panettiere unveiled yet another transformation in a Sept. 19 Instagram post, debuting green roots that blended into her bright blush locks.

Love my new watermelon vibes up top!" she captioned the photos, going on to thank hair colorist Erick Orellana for the two-tone look.

Pinkett Smith just added a little more pink to her last name.

 In honor of her 52nd birthday, the Red Table Talk host took to Instagram on Sept. 18 to show off a new rose gold hair color. 

"This ain't noth'n but a birthday sherbet surprise," she captioned the post, "within a Virgo sunrise."

Now that is giving body-ody-ody-ody-ody.

The Grammy winner showed off the results of her ongoing fitness journey in a "gym recap" video she posted to Instagram.

"What's up ya'll, it's Megan Thee Stallion, aka the hot girl coach," the musician said in the clip, before revealing each exercise she does. "And bitch, the results have been resulting. The word for the rest of the year is consistency."

In the video, the "Hot Girl Summer" singer performs moves such as deadlifts, jump-rope, forward lunges and mountain climbers.

"This s--t burn like a motherf--ker," she admitted. "But I know you see them thighs popping."

Anyone else craving coffee now? 

The "You & I" singer refreshed her hair ahead of the fall season, opting for a warm bronde hue. Ora's autumnal color was courtesy of hair stylist Dimitris Giannetos, who unveiled The Masked Singer judge's new look on his Instagram page.

"Chai latte highlights," Giannetos captioned the pic.