The Tac is T/Y in my reference (Tan/yellow stripe) up to connector C228, where it goes White/pink, into the VMM, then back out as T/Y. to the gauge.
Wire Color Code Identification
BK : Black
BL : Blue
BR : Brown
DB : Dark Blue
DG : Dark Green
GY : Gray
GN : Green
LB : Light Blue
LG : Light Green
PK : Pink
O : Orange
P : Purple
R : Red
T : Tan
V : Violet
W : White
Y : Yellow
Where two colors are shown for a wire, first is basic color and second is stripe marking (tracer).
For example, BR/O is brown with orange stripe.