For the most part, 4,000k vs 5,000k is up to the personal look that you are seeking for your mat.

I had one mat that had mostly earth tones in it so the 4,000k worked out fine for that color scheme. I had another store where I installed 5,000k because the store's basic coloring was more white, stainless, and mauve accents. Personally, I definitely prefer the 5,000k. They call 5,000k a "daylight" bulb for a reason....It mimics daylight. You get more "pop" for the lumens, and the slight bluish tint will make your customer's whites look whiter…especially over the folding tables.

There's also another less tangible benefit to having a WELL lit store with Daylight bulbs....They help ward off depression. A well lit store could even help with your worker's attitudes, not to mention your customers finding your mat more appealing even if they're not sure why. It's all about making customers feel good about your mat, and ample lighting that mimics real daylight is just another plus. 

That said, I did try 6,000k in a back room and it was horrible....way too blue. A cold feeling.

Check Out: Light Therapy & The Best SAD Lamps to Boost Your Seasonal Depression

Started back in 1976 rehabbing a run down old mat. Only 3 washers were working properly, and only 2 lights out of 30 actually worked. The floor was buckled up from years of water leaks. Some of the machines were ancient, even for way back then. After I renovated it, that store broke-even after 3 months.