The blue liquid you're referring to is likely the coolant used in refrigeration systems. In a typical refrigerator, the coolant is contained within a closed system of pipes and coils called the refrigerant circuit. The refrigerant circulates through these pipes, absorbing heat from the inside of the refrigerator and releasing it outside, which cools the interior of the fridge.
The specific location of the blue liquid inside the refrigerator depends on the design and type of refrigerator. In modern refrigerators, the coolant is usually contained within the walls or back panel of the unit. It is not directly visible or accessible to users.
If you are seeing a blue liquid inside your refrigerator, it may indicate a problem with the refrigerant circuit or a leak in the system. In such cases, it is recommended to contact a professional technician to inspect and repair the refrigerator.