I don't know where you got this info from. The original reason for adding lead to gas was to increase octane and prevent ignition knocking in higher compression engines. Subsequently, it was discovered that the lead would deposit on the valve seats and protect them from impact erosion. This resulted in car companies buildin cast iron heads without hardened valve seats as they were not needed when using leaded gas.
Sice leaded gas was discontinued, the available lead substitute additives are designed to protect those old vehicles, which were designed with soft valve seats, by depositing a coating on the valve seats. Naturally, the additive, like lead, does not know where it is being deposited, so it coats everything.
2 cycle engines have no valve seats to protect and aluminum 4 cycle heads use hardened valve seat inserts which do not erode.
The color you see when you open your engine is the deposited additive. It changes the color of the surfaces but does not decrease the rate of build up of deposits. In fact, it increases the build up.