test: add ColorAttributes unit tests

Add 16 tests covering constructor behavior, fill/stroke flags and colors,
null color handling, ID constant, Attributes interface, toString output,
and instance independence.

Closes #7

pom.xml

@@ -15,7 +15,6 @@
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-compiler-plugin</artifactId>
-                <version>3.13.0</version>
                 <configuration>
                     <source>16</source>
                     <target>16</target>
@@ -29,7 +28,7 @@
             <plugin>
                 <groupId>org.jacoco</groupId>
                 <artifactId>jacoco-maven-plugin</artifactId>
-                <version>0.8.13</version>
+                <version>0.8.11</version>
                 <executions>
                     <execution>
                         <goals>
@@ -71,13 +70,13 @@
         <dependency>
             <groupId>org.slf4j</groupId>
             <artifactId>slf4j-api</artifactId>
-            <version>2.0.16</version>
+            <version>RELEASE</version>
         </dependency>
 
         <dependency>
             <groupId>ch.qos.logback</groupId>
             <artifactId>logback-classic</artifactId>
-            <version>1.5.12</version>
+            <version>RELEASE</version>
         </dependency>
 
         <dependency>