Source option not showing up in Color Match on Photoshop

Hello,

I'm new to Photoshop, so I apologise in advance if I'm missing an obvious step! I'm trying to colour match an exact item. I selected the colour I wanted with the rectangle marquee tool on one tab, then I selected the colour range on the destination photo. I copied the layer. When I choose colour match, there isn't an option to choose the source from the target colour that I want (see screenshot - I need the G10 Epoxy source option to show up). 

Thanks in advance!