Coolant is sold in several colors and specifications, and the differences are not cosmetic. What separates them is the additive package protecting the metals inside the engine.
Antifreeze is the easy part of the job
The base fluid is usually ethylene glycol mixed with water, and that mixture handles freeze protection and raises the boiling point under system pressure.
Almost every coolant on the shelf performs that function similarly. Freeze protection depends on the ratio of glycol to water, not on the brand or color.
The demanding requirement is preventing corrosion in a system containing iron, aluminum, copper, brass, solder and rubber, all at high temperature for years.
Inhibitor chemistry defines the type
Older conventional coolants use inorganic additives such as silicates and phosphates, which form a protective film quickly on metal surfaces.
Organic acid technology coolants use carboxylates instead, which act more slowly but deplete far more gradually, which is why they carry long service intervals.
Hybrid formulations combine both approaches, and manufacturers specify particular versions because their engines contain particular alloys and sealing materials.
Mixing can neutralize the protection
Combining silicate and carboxylate chemistries can cause the additives to react with each other rather than protect the metal, dropping out as a gel or precipitate.
The result blocks radiator tubes and heater cores, which are the narrowest passages in the system and the hardest to clean.
The mixture will still resist freezing, so the failure is invisible until an overheating problem or a heater that no longer produces warmth appears.
Color is not a specification
Dye is added for leak identification and marketing, and different manufacturers have used the same color for different chemistries at different times.
Universal coolants exist and are formulated for compatibility across types, but a universal product is a compromise rather than a match for a specific factory specification.
The reliable identifier is the manufacturer specification number printed on the container and listed in the owner's manual, not the appearance of the fluid.
Depletion happens whether or not the fluid looks bad
Inhibitors are consumed as they do their work, so coolant reaches the end of its life by chemistry rather than by dirt or discoloration.
Test strips measure freeze point and reserve alkalinity, giving an indication of whether the additive package is still active.
Correcting a wrong fill means a full flush rather than a drain, since a substantial share of the old fluid remains in the block and heater core after draining.