The backgrounds of Nodes are currently slightly transparent. You can see the grid bleeding through in the following capture:

This isn't on purpose. Until fairly recently the only way we could have items like this be antialiased was to overprint multiple times with a jitter and low alpha, a process that only gives about 65% opacity. But now we can draw these with our widget shader which can be both opaque and AA. Node drawing is currently using this new shader, but in a "legacy" mode that emulates the old behavior.

This patch switches to using the shader in non-legacy mode so we can get opaque backgrounds. Not only does this mean the grid does not bleed through, but also that the colors will now exactly match the color specified in the theme - since it is no longer mixed with the background color.

However, this does mean the colors are slightly different until we change the theme settings, which I understand we are planning to do with 3.0 anyway. To illustrate this color vibrancy issue, the following shows the current colors looking more muted than what is defined:

The following shows what it looks like after this patch is applied, with colors matching the theme settings but also looking a bit too bright until we alter the theme.