allow user to use hex colors in config (#486)

crates/nu-command/src/viewers/color_config.rs

@@ -15,6 +15,15 @@ use std::collections::HashMap;
 // }
 
 pub fn lookup_ansi_color_style(s: String) -> Style {
+    if s.starts_with('#') {
+        match color_from_hex(&s) {
+            Ok(c) => match c {
+                Some(c) => c.normal(),
+                None => Style::default(),
+            },
+            Err(_) => Style::default(),
+        }
+    } else {
         match s.as_str() {
             "g" | "green" => Color::Green.normal(),
             "gb" | "green_bold" => Color::Green.bold(),
@@ -82,6 +91,22 @@ pub fn lookup_ansi_color_style(s: String) -> Style {
             "wst" | "white_strike" => Color::White.strikethrough(),
             _ => Color::White.normal(),
         }
+    }
+}
+
+fn color_from_hex(hex_color: &str) -> std::result::Result<Option<Color>, std::num::ParseIntError> {
+    // right now we only allow hex colors with hashtag and 6 characters
+    let trimmed = hex_color.trim_matches('#');
+    if trimmed.len() != 6 {
+        Ok(None)
+    } else {
+        // make a nu_ansi_term::Color::Rgb color by converting hex to decimal
+        Ok(Some(Color::Rgb(
+            u8::from_str_radix(&trimmed[..2], 16)?,
+            u8::from_str_radix(&trimmed[2..4], 16)?,
+            u8::from_str_radix(&trimmed[4..6], 16)?,
+        )))
+    }
 }
 
 // TODO: i'm not sure how this ever worked but leaving it in case it's used elsewhere but not implemented yet