Coles Financial Services, Rolled out some but not all digital wallet support to their credit card products today. The products referred to in the industry as a co-branded card are issued by Citigroup.
Unfortunately there is no Google Pay support this is most likely not a Coles Financial Services problem and more of a Citigroup problem who issues the cards on their behalf.
Citibank, in Australia has not rolled out Google Pay on even their products which means on a co-branded product you’re highly unlikely to be able to see the functionality as well.
Hopefully sometime in the near future the decision not to support Google Pay by Citibank will be resolved and Google Pay can then make it down the chain to co-branded card products issued by Citigroup.