fix: stop using ANSI blue (#2421)

- One less color.
- Replaced with cyan which looks better next to other cyan components.

codex-rs/tui/styles.md

@@ -7,16 +7,15 @@
 # Foreground colors
 
 - **Default:** Most of the time, just use the default foreground color. `reset` can help get it back.
-- **Selection:** Use ANSI `blue`. (Ed & AE want to make this cyan too, but we'll do that in a followup since it's riskier in different themes.)
-- **User input tips and status indicators:** Use ANSI `cyan`.
+- **User input tips, selection, and status indicators:** Use ANSI `cyan`.
 - **Success and additions:** Use ANSI `green`.
 - **Errors, failures and deletions:** Use ANSI `red`.
 - **Codex:** Use ANSI `magenta`.
 
 # Avoid
 
-- Avoid custom colors because there's no guarantee that they'll contrast well or look good in various terminal color themes.
+- Avoid custom colors because there's no guarantee that they'll contrast well or look good in various terminal color themes. (`shimmer.rs` is an exception that works well because we take the default colors and just adjust their levels.)
 - Avoid ANSI `black` & `white` as foreground colors because the default terminal theme color will do a better job. (Use `reset` if you need to in order to get those.) The exception is if you need contrast rendering over a manually colored background.
-- Avoid ANSI `yellow` because for now the style guide doesn't use it. Prefer a foreground color mentioned above.
+- Avoid ANSI `blue` and `yellow` because for now the style guide doesn't use them. Prefer a foreground color mentioned above.
 
 (There are some rules to try to catch this in `clippy.toml`.)