feat(performance-matrix): color code FPS values based on thresholds

Color-code the FPS readings in the performance matrix plugin to provide
visually clear feedback regarding the frame rate status. Green indicates
good performance (above 60 FPS), yellow represents acceptable performance
(30 to 60 FPS), and red signifies poor performance (below 30 FPS).

src/plugins/performance_matrix.rs

@@ -35,12 +35,12 @@ impl PerformanceBundle {
         };
         PerformanceBundle {
             text: TextBundle::from_sections([
-                text_section(Color::GREEN.with_a(ALPHA), "FPS     : "),
-                text_section(Color::CYAN.with_a(ALPHA), ""),
-                text_section(Color::GREEN.with_a(ALPHA), "FPS(SMA): "),
-                text_section(Color::CYAN.with_a(ALPHA), ""),
-                text_section(Color::GREEN.with_a(ALPHA), "FPS(EMA): "),
-                text_section(Color::CYAN.with_a(ALPHA), ""),
+                text_section(Color::CYAN.with_a(ALPHA), "FPS     : "),
+                text_section(Color::default().with_a(ALPHA), ""),
+                text_section(Color::CYAN.with_a(ALPHA), "FPS(SMA): "),
+                text_section(Color::default().with_a(ALPHA), ""),
+                text_section(Color::CYAN.with_a(ALPHA), "FPS(EMA): "),
+                text_section(Color::default().with_a(ALPHA), ""),
             ])
             .with_style(Style {
                 position_type: PositionType::Absolute,
@@ -64,13 +64,22 @@ fn update_performance_matrix(
     let mut text = query.single_mut();
     if let Some(fps) = diagnostics.get(&FrameTimeDiagnosticsPlugin::FPS) {
         if let Some(raw) = fps.value() {
-            text.sections[1].value = format!("{raw:.2}\n");
+            update_fps(raw, &mut text.sections[1]);
         }
         if let Some(sma) = fps.average() {
-            text.sections[3].value = format!("{sma:.2}\n");
+            update_fps(sma, &mut text.sections[3]);
         }
         if let Some(ema) = fps.smoothed() {
-            text.sections[5].value = format!("{ema:.2}\n");
+            update_fps(ema, &mut text.sections[5]);
         }
     }
 }
+
+fn update_fps(value: f64, section: &mut TextSection) {
+    section.value = format!("{value:.2}\n");
+    section.style.color = match value {
+        v if v < 30.0 => Color::RED,
+        v if v < 60.0 => Color::YELLOW,
+        _ => Color::GREEN,
+    };
+}