1964 barracuda dash color

My 1964 Barracuda is at the painter. The exterior color is red. The interior is the same color as the exterior. The top of the dash however is a duller, non reflective red. I need to know what to mix with the exterior color to create this flat color. Also, since it's been so long, I don't remember if the plastic vents on top of the dash matched the duller color, or did they match the rest of the car?

Thanks for your help,
Dave