fix: Prevent global group from adversely affecting color. (#2703)

Co-authored-by: ylemkimon <y@ylem.kim>

src/parseTree.js

@@ -18,10 +18,16 @@ const parseTree = function(toParse: string, settings: Settings): AnyParseNode[]
         throw new TypeError('KaTeX can only parse string typed expression');
     }
     const parser = new Parser(toParse, settings);
+
     // Blank out any \df@tag to avoid spurious "Duplicate \tag" errors
     delete parser.gullet.macros.current["\\df@tag"];
+
     let tree = parser.parse();
 
+    // Prevent a color definition from persisting between calls to katex.render().
+    delete parser.gullet.macros.current["\\current@color"];
+    delete parser.gullet.macros.current["\\color"];
+
     // If the input used \tag, it will set the \df@tag macro to the tag.
     // In this case, we separately parse the tag and wrap the tree.
     if (parser.gullet.macros.get("\\df@tag")) {

test/katex-spec.js

@@ -869,6 +869,7 @@ describe("A color parser", function() {
         const macros = {};
         expect(oldColorExpression).toParseLike(r`\textcolor{#fA6}{x}y`, {
             colorIsTextColor: true,
+            globalGroup: true,
             macros: macros,
         });
         expect(macros).toEqual({});