Multiple Artboard solid fill layer change

Thanks for the replies. If i go with the smart object option the only issue I can see is that I have to open that in a new window and cant eyedrop colours from the products on the original artboards and seamlessly decide on a colour that looks best since you have to save the smart object file before it changes on the original artboards. My current method makes it easy to drag around my cursor on the colour picker to decide on a nice background colour that matches without needing to have a new window open or saving to see the new colour. 
Im not sure I understand what your saying in suggestion one.

I was going to suggest the same as @r-bin – a linked smart object would auto-update.

Otherwise, a script could find and update the solid fill layer, however, the layer structure would need to be understood and hopefully the files would be consistent.

I'm not sure if this will suit you, but try it.

1. Instead of a SolidColor layer with a pixel mask, you can use a Shape layer with a sufficiently large vector mask and the current pixel mask. In this case, if the layers are linked, you can execute the "select linked" command. After that, in the options panel for the Pen or Shape tools, select the desired fill color. In this case, the color will change for all selected layers.

2. You can also turn one SolidColor layer into a smart object, and replace the rest with copies of it (via Ctrl+J). When the color inside any such smart object changes, its copies will change automatically. There is no need to link or select anything.