Add a new gemstone

docs/gemstones/string_color.md

@@ -0,0 +1,96 @@
+---
+titie: About the color of the string
+author: tianci li
+contributors: Steven Spencer
+tested with: 8.6, 9.0
+tags:
+  - bash
+  - color
+---
+
+# Introduction
+
+When we download bash scripts that have been written by others in our daily work, sometimes some key strings are marked with special colors. How can this effect be achieved by writing in a script?
+
+## Font color
+
+| **color code** | **describe** |
+|    :---:       |    :---:     |
+|  30            |    black     |
+|  31            |     red      |
+|  32            |    green     |
+|  33            |    yellow    |
+|  34            |     blue     | 
+|  35            |     purple   |
+|  36            |   Dark green |
+|  37            |    white     |
+
+## Background color of font
+
+| **Background color code** | **describe** |
+|    :---:       |    :---:     |
+|     40         |    black     |
+|     41         |    Crimson   |
+|     42         |    green     |
+|     43         |    yellow    |
+|     44         |    blue      |
+|     45         |    purple    |
+|     46         |  Dark green  |
+|     47         |   white      |
+
+## Display mode
+
+| **code** | **describe** |
+|  :---:   |    :---:     |
+|    0     |Terminal default settings|
+|    1     |Highlight|
+|    4     |Underline|
+|    5     |Currsor blinks|
+|    7     |Reverse display|
+|    8     | hide |
+
+## Mode of execution
+
+* **\033[1;31;40m**
+"1" indicates the display mode, which is optional. "31" indicates the font color. "40m" indicates the font background color
+
+* **\033[0m**
+Restore the terminal default color, that is, cancel the color setting
+
+## Script example
+
+We can write a script to observe the color change.
+
+```bash
+#!/bin/bash
+# Font color cycle
+for color1 in {31..37}
+    do
+        echo -e "\033[0;${color1};40m---hello! world---\033[0m"
+    done
+
+echo "-------"
+
+# Background color cycle
+for color2 in {40..47}
+    do
+        echo -e "\033[30;${color2}m---hello! world---\033[0m"
+    done
+
+echo "-------"
+
+# Cycle of display mode
+for color3 in 0 1 4 5 7 8
+    do
+        echo -e "\033[${color3};37;40m---hello! world---\033[0m"
+    done
+```
+
+```bash
+Shell > chmod a+x color_set.sh
+Shell > ./color_set.sh
+```
+
+The effect is as follows:
+
+![image1](./images/string_color_image1.png)