I've been playing around with my QGIS Bonn (3.2.3) and I have a question regarding styles/symbology/colours.
Is it possible in QGIS to set one colour/style to multiple layers at once?
Yes, it is possible. In QGIS 3.6, right-click the layer that you want keep its style
-> Styles -> Copy style -> Select Symbology
Then go to other layer select them all using SHIFT and left-click on your mouse, then right-click any place above the selected layer
-> Paste Style
All of them will have the same style: