update docs for color option

Cargo.lock

@@ -100,7 +100,7 @@ dependencies = [
 
 [[package]]
 name = "clock-tui"
-version = "0.2.0"
+version = "0.2.1"
 dependencies = [
  "chrono",
  "clap",

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "clock-tui"
-version = "0.2.0"
+version = "0.2.1"
 edition = "2021"
 license = "MIT"
 description = "A clock app in terminal"

README.md

@@ -67,7 +67,7 @@ You can press `Space` key to _pause_ and _resume_ the stopwatch.
 
 You can customize the styles.
 
-* Size
+### Size
 
 You can use `-s` or `--size` option to custome clock size, for example:
 
@@ -75,12 +75,14 @@ You can use `-s` or `--size` option to custome clock size, for example:
 $ tclock -s 2
 ```
 
-* Color
+### Color
 
 You can use `-c` or `--color` to set clock forground color, for exmaple:
 
 ```shell
-# color name
+# color name, any one of: 
+# Black, Red, Green, Yellow, Blue, Magenta, Cyan, Gray, DarkGray, LightRed,
+# LightGreen, LightYellow, LightBlue, LightMagenta, LightCyan, White
 $ tclock -c yellow
 
 # or hex color

src/app.rs

@@ -38,8 +38,12 @@ pub(crate) enum Mode {
 pub(crate) struct App {
     #[clap(subcommand)]
     pub mode: Option<Mode>,
+    /// Forground color of the clock, possible values are:
+    ///     a) Any one of: Black, Red, Green, Yellow, Blue, Magenta, Cyan, Gray, DarkGray, LightRed, LightGreen, LightYellow, LightBlue, LightMagenta, LightCyan, White.
+    ///     b) Hexadecimal color code: #RRGGBB.
     #[clap(short, long, value_parser = parse_color, default_value = "green")]
     pub color: Color,
+    /// Size of the clock, should be a positive integer (>=1).
     #[clap(short, long, value_parser, default_value = "1")]
     pub size: u16,