Fix green colors becoming darker in various examples (#12328)

# Objective

Fixes #12225

Prior to the `bevy_color` port, `GREEN` used to mean "full green." But
it is now a much darker color matching the css1 spec.

## Solution

Change usages of `basic::GREEN` or `css::GREEN` to `LIME` to restore the
examples to their former colors.

This also removes the duplicate definition of `GREEN` from `css`. (it
was already re-exported from `basic`)

## Note

A lot of these examples could use nicer colors. I'm not trying to do
that here.

"Dark Grey" will be tackled separately and has its own tracking issue.