Problem with reference image - Changes to alpha does not change transparency I need to decrease the  reference image opacity, but when I decrease the      alpha in colour in Image tab (in properties), the image does not become transparent.

Image tab displaying the change in alpha


The reference image (a bowling pin), which is opaque, not transparent
Change opacity in the data properties panel transparency subpanel


Change from object properties to data properties, set opacity

The other answer popped up while making gif.  Thought I'd post as it is from a build of 2.83 and has a slightly different location for opacity setting.