Using a shader that works like Phong, what would be the difference between painted Metal and plastic?

I seem to remember reading in books years ago, that I no longer have access to, the following:

• Specular color for painted metal is same color as the paint.
• Specular color for plastic is always white.
• Ambient for metal should be darker than for plastic.

This also seems to correlate with what I see when I observe objects (in real world)

But I tried to verify this also by checking the Internet, and found conflicting versions, some said the complete opposite.

So what is true?

Using a shader that works like Phong, what would be the difference between painted Metal and plastic?

I seem to remember reading in books years ago, that I no longer have access to, the following:

• Specular color for painted metal is same color as the paint.
• Specular color for plastic is always white.
• Ambient for metal should be darker than for plastic.

This also seems to correlate with what I see when I observe objects (in real world)

But I tried to verify this also by checking the Internet, and found conflicting versions, some said the complete opposite.

So what is true?