[wpilib] Add hex string constructor to Color and Color8Bit (#5063)

Co-authored-by: Tyler Veness <calcmogul@gmail.com>

wpilibj/src/main/java/edu/wpi/first/wpilibj/util/Color.java

@@ -21,6 +21,13 @@ public class Color {
   public final double blue;
   private String m_name;
 
+  /** Constructs a default color (black). */
+  public Color() {
+    red = 0.0;
+    green = 0.0;
+    blue = 0.0;
+  }
+
   /**
    * Constructs a Color from doubles.
    *
@@ -69,6 +76,22 @@ public class Color {
     this.m_name = name;
   }
 
+  /**
+   * Constructs a Color from a hex string.
+   *
+   * @param hexString a string of the format <code>#RRGGBB</code>
+   * @throws IllegalArgumentException if the hex string is invalid.
+   */
+  public Color(String hexString) {
+    if (hexString.length() != 7 || !hexString.startsWith("#")) {
+      throw new IllegalArgumentException("Invalid hex string \"" + hexString + "\"");
+    }
+
+    this.red = Integer.valueOf(hexString.substring(1, 3), 16) / 255.0;
+    this.green = Integer.valueOf(hexString.substring(3, 5), 16) / 255.0;
+    this.blue = Integer.valueOf(hexString.substring(5, 7), 16) / 255.0;
+  }
+
   /**
    * Creates a Color from HSV values.
    *

wpilibj/src/main/java/edu/wpi/first/wpilibj/util/Color8Bit.java

@@ -14,6 +14,13 @@ public class Color8Bit {
   public final int green;
   public final int blue;
 
+  /** Constructs a default color (black). */
+  public Color8Bit() {
+    red = 0;
+    green = 0;
+    blue = 0;
+  }
+
   /**
    * Constructs a Color8Bit.
    *
@@ -36,6 +43,22 @@ public class Color8Bit {
     this((int) (color.red * 255), (int) (color.green * 255), (int) (color.blue * 255));
   }
 
+  /**
+   * Constructs a Color8Bit from a hex string.
+   *
+   * @param hexString a string of the format <code>#RRGGBB</code>
+   * @throws IllegalArgumentException if the hex string is invalid.
+   */
+  public Color8Bit(String hexString) {
+    if (hexString.length() != 7 || !hexString.startsWith("#")) {
+      throw new IllegalArgumentException("Invalid hex string \"" + hexString + "\"");
+    }
+
+    this.red = Integer.valueOf(hexString.substring(1, 3), 16);
+    this.green = Integer.valueOf(hexString.substring(3, 5), 16);
+    this.blue = Integer.valueOf(hexString.substring(5, 7), 16);
+  }
+
   @Override
   public boolean equals(Object other) {
     if (this == other) {