Be patient with me now clutchc. I think the colors have me confused between what you showed me and the picture I posted, which is the original fan wire colors. How about this and you tell me if I'm right or wrong using the picture I posted.
Black= Ground
Red= +12V
Yellow= Tach
Blue= PWM
What I am doing is replacing the stock cpu cooler with an Arctic Freezer 13 CO. Their four wires→
https://support.arctic.ac/index.php?p=freezer13co&doc=faq&lang=en
are what I'm trying to sort out to the correct Dell header.