[Feature] color legend per report

## Request
Add the color rule to reports configuration

## Example
```
task.ready.color.due.today=blue
task.ready.color.due=
```

## Use case
I'm sure a lot of thoughts went into the current color choices (`task color legend`) and for reports such as `task list`, that works alright.

I also found that I was able to use TaskWarrior much more efficiently once I adopted [dave yarwood's Inbox zero](https://blog.djy.io/taskwarrior-where-have-you-been-all-my-life/) strategy with `task ready`, which I set as my default command (`task config default.command ready`). I now have the habit of setting due and scheduled dates to all my tasks.

Now, whenever I run `task`, I see all my tasks in red (or orange, but the colors look very similar for me using the solarized light theme)
.

I would like to override rules for this report only. Or if someone has a better suggestion, since I'm not a designer, I'd love to hear about your opinion on how to make colors more meaningful in a task inbox zero environment.