Display palette and colors for dark and light themes in storybook (#29848)

packages/grafana-ui/src/components/ThemeColors/Colors.story.tsx

+import React from 'react';
+import { Colors } from './Colors';
+
+export default {
+  title: 'Docs Overview/Colors',
+  component: Colors,
+  decorators: [],
+  parameters: {
+    options: {
+      showPanel: false,
+    },
+    docs: {},
+  },
+};
+
+export const ColorsDemo = () => {
+  return <Colors />;
+};

packages/grafana-ui/src/components/ThemeColors/Colors.tsx

+import React from 'react';
+import { css, cx } from 'emotion';
+import darkTheme from '../../themes/dark';
+import lightTheme from '../../themes/light';
+import { useStyles } from '../../themes';
+
+export const Colors = () => {
+  const styles = useStyles(getStyles);
+  const renderColors = (color: any) => {
+    return Object.entries(color)
+      .sort((a, b) => a[0].localeCompare(b[0]))
+      .map(([name, color]: [string, any]) => {
+        return (
+          <div key={name} className={styles.wrapper}>
+            <span className={styles.name}>
+              {name} ({color})
+            </span>
+            <span
+              className={cx(
+                styles.color,
+                css`
+                  background: ${color};
+                `
+              )}
+            />
+          </div>
+        );
+      });
+  };
+
+  return (
+    <div className={styles.container}>
+      <div>
+        <h2>Light theme</h2>
+        <h3 className={styles.subheader}>Palette</h3>
+        {renderColors(lightTheme.palette)}
+        <h3 className={styles.subheader}>Colors</h3>
+        {renderColors(lightTheme.colors)}
+      </div>
+
+      <div>
+        <h2>Dark theme</h2>
+        <h3 className={styles.subheader}>Palette</h3>
+        {renderColors(darkTheme.palette)}
+        <h3 className={styles.subheader}>Colors</h3>
+        {renderColors(darkTheme.colors)}
+      </div>
+    </div>
+  );
+};
+
+const getStyles = () => {
+  return {
+    subheader: css`
+      margin: 20px 0;
+    `,
+    container: css`
+      display: flex;
+      justify-content: space-around;
+      width: 100%;
+    `,
+    wrapper: css`
+      display: flex;
+      align-items: center;
+    `,
+    name: css`
+      width: 250px;
+    `,
+    color: css`
+      display: inline-block;
+      width: 50px;
+      height: 50px;
+    `,
+  };
+};