If sticking to Tamiya, to me that looks very close to their desert yellow with perhaps some yellow and white?
Thing is with their dark yellow, I always found it had a green or olive tinge to it. If you mix in a brown or tan the result will have a grey tone to it, which may or may not be what you want.
Why do I say grey? Properties of primary colours - when you mix blue, red and yellow you will get black. Dark yellow has yellow and blue already and when you add tan, brown or orange (all of which contain a percentage of red) the result will be a shade of black - a grey.
Doogs, if you think it is Giallo Mimetico 4, why not just purchase a bottle. I know saving money on a paint colour you may never ever use again, but there is consideration of paint wasted in trying to mix your own.