Well that shirt looks more yellow than Old Gold. The football is actually a very dark/browny tinge of Gold, a bit darker than Old Gold.
If I was doing the graphic design, I would actually remove the jersey.
The reason being is that the kangaroo has to be red - and the real jersey will be predominantly red (not gold as shown) - so when our eyes are drawn to the head/jersey it actually is distracting because we're not focusing on the red - the only way to resolve this is to remove the jersey.
What would work best is:
- a SOLID RED (my preference is Cardinal) KANGAROO - no jersey
- potentially holding an OLD GOLD football
- with BLACK as the outline colour around the edges
- with 'WA' written in OLD GOLD
- and REDS in CARDINAL RED
Thus the black and old gold 'trim' the red and we focus on the RED. Also around the WA REDS logo, you could alternatively use Black (outer) & Old Gold (inner) around the border edges as a dual colour outline.