Fixed @color to accept a blank value

execution_context.go

@@ -926,7 +926,7 @@ func (c *ExecutionContext) setCmd(input string) {
 
 func (c *ExecutionContext) colorCmd(input string) {
 
-	r, _ := regexp.Compile(`^@color\pZ+([^=]*[^=\pZ]{1})\pZ*=\pZ*(.*[^\pZ]{1})\pZ*$`)
+	r, _ := regexp.Compile(`^@color\pZ+([^=]*[^=\pZ]{1})\pZ*=\pZ*(.*[^\pZ])\pZ*$`)
 	params := r.FindStringSubmatch(input)
 	if params == nil {
 		return