This is a visual issue. Grey background color isn't consistent throughout the app.

If you open Today, or Next, or Tomorrow, etc., there’s a nice grey background color which creates a very nice contrast and serves as a visual aid (separating visually between tasks/contexts/projects; especially useful when tasks are numerous).

However, when you open a specific task, or a context, or any of your projects, this background color gets replaced with slightly brighter one, which doesn’t create the same level of contrast.

My suggestion is to use only one background color throughout the app, and specifically the darker one of the two greys, since it is much more useful and helps in visual differentiation of tasks. And it is a good practice to be consistent and use only one color for a specific interface part.