An employee secures the lid of a Valspar Corp. paint can for a customer inside a Lowe's store in Burbank, California.

Sherwin-Williams is deepening a decades-old relationship with Lowe's, making it the only nationwide home center to offer Sherwin's popular brands including Minwax, Cabot and Thompson's Water Seal.

Sherwin-Williams will continue to operate its own stores.

On the day the deal was announced, Lowe's also reported quarterly earnings that fell short as profit margins were squeezed. Lowe's share prices were down more than 7 percent Wednesday morning.

News of the deal comes as Lowe's fights to keep pace with rival Home Depot, which recently revealed its plans to partner with Tesla to sell solar panels in its stores. Lowe's and Home Depot compete within the industry to win the best brands that, in turn, will attract more shoppers. Last October, for example, Stanley Black & Decker tapped Lowe's as the next retail destination for its Craftsman tool brand.

In securing the deal with Sherwin-Williams, Lowe's aims to be the go-to retailer for do-it-yourself shoppers. That category has been growing, and painting is consistently a top DIY project.

For home improvement stores like Lowe's, the paint category helps bolster sales because paint shoppers tend to add other items to their baskets, such as brushes and tape. Lowe's goal is to get shoppers to spend more per trip.

"We do a tremendous amount of research related to customer preferences," said Lowe's Chief Customer Officer Mike McDermott. "And through that analysis we draw insights, which have led us to some of the most important brands" that shoppers are requesting, Sherwin-Williams being one of those.

"We have been very strategic in our approach," he added. "We don't do these exclusive partnerships with every vendor." In doubling down on a deal with Sherwin-Williams, Lowe's will phase out other paint brands in stores over time.

Lowe's will also be ramping up investments in its stores, specifically in the paint department.

The company is adapting its paint service model and training employees more about Sherwin-Williams' merchandise. Refurbished locations will soon include a new paint product display and redesigned "paint desks," where workers for that department normally sit, ready to answer shoppers' questions.

Late last year, Lowe's was targeted by activist investor D.E. Shaw & Co. for not performing well enough relative to its peers. The company said it is working toward changing those perceptions.

"The biggest opportunity we have in stores is to improve selection and the product experience for our customers," McDermott said. "We see greater opportunity for efficiency. ... Customers continue to tell us they want the best brands and the highest level of quality."

Lowe's shares have climbed about 25 percent from a year ago, while Home Depot's stock is up roughly 27 percent over the same period.

Correction: This story was updated to clarify that the deal with Lowe's involves exclusivity for certain Sherwin-Williams products.