New dimmer theme

[ansel1]

I'd like to propose a new theme, maybe called "dim" or "contrast" or something...

The first screenshot is the current default theme. The second is the proposed theme. The main change is that blue replaces cyan, and attr values use gray. This has the effect of making the attributes fade back a little more, and the message pop out more. To my eye, this makes the logs a little easier to scan. I can prepare a PR if interested.

current default:

dim: