This is for sure the longest title of any of my posts, but it's the only way to summarize the topic. What I want to discuss are the ways in which you can highlight portions of your data or elements of the graph, by adding a grey background to a portion of your graphic. By the end I hope you will find this approach quite useful in multiple cases.

Let's start by talking about plotting results of multiple conditions in a single graph.

Let's take for example the graph from Sung et al. 2016:

Graph depicts following conditions:

(1) basal, (2) antinomycin and (3) H2O2; on top of that each of those treatments was applied in control and park25 knock down. So overall 6 conditions.

In the original figure the treatment is indicated by the outline of the bar: black for basal, red for antinomycin and blue for H2O2. Not too bad, but probably too subtle. Of course one way would be to make the whole bar in color, but then you need to find a way to discriminate between control and knock down (best way is to use two different saturations of the same color).

The more attractive alternative is to introduce a grey bar that will create a distinction between the different conditions:


Looks much cleaner and we can avoid using multiple labels for control and park25.

Second example in which using grey background in portion of the figure is to highlight portion of the primary data. Here, Leal et al. 2016 show levels of different proteins in control and knock down conditions:

Some of them are part of the gamma secretase components. The way authors chose to highlight them is quite space demanding and leave a lot of white space. There is nothing really wrong about keeping some white space for your panels "to breathe", but in this case it can be done more efficiently, by using a grey bar:


Finally, "the great grey bar" can be used for highlighting the important part of the figure (distinguishing it from the rest). Like in this another example from Leal et al.:


Here the drug treatment is a bit lost between all the other labels, when in fact it should be highlighted. This can be easily fixed: