The new resilient floor was installed perfectly. The required maintenance program was explained to the customer in full detail. The customer, in turn, conscientiously performed preventative maintenance such as applying proper floor protectors to furniture, adding window coverings to guard against excess sunlight exposure, and laying walk-off mats near entrances for people to wipe their feet. So where did that yellow stuff on the floor come from?

So where did that yellow stuff on the floor come from?