This support note explains Yellow, Pink and White colour highlighting in the Receiving register.
Yellow : Purchase is an ORDER in MYOB
Pink : Overdue orders (Promised Date is less than today's date)
White : Purchase is a Bill in MYOB and is not overdue
Open : No stock received
Closed : All stock received or order has been marked as no further stock to receive
Split : Partial stock has been received
For overdue (pink highlighting), please turn on the preference "Highlight Overdue Sale/Receive Orders" found in Tools > Preferences > General Tab.
Note: This preference is a per user preference.