public void tuk(){

btn.setText("Xposed должен сделать данный текст красным и изменить текст на Красный");

        }

package ru.kiceargy.xposedtest;

import android.graphics.Color;
import android.widget.Button;
import de.robv.android.xposed.IXposedHookLoadPackage;
import de.robv.android.xposed.XC_MethodHook;
import de.robv.android.xposed.callbacks.XC_LoadPackage;
import static de.robv.android.xposed.XposedHelpers.findAndHookMethod;
/*
 * Created by k1ceargy on 23.06.18 (macOS 10.12)
 * */
public class Main implements IXposedHookLoadPackage {



        @Override
        public void handleLoadPackage(XC_LoadPackage.LoadPackageParam lpparam) throws Throwable {
            if (!lpparam.packageName.equals("ru.kiceargy.line.remote_controller")) {
                return;
            }

            findAndHookMethod("ru.kiceargy.line.remote_controller", lpparam.classLoader,
                    "tuk", new XC_MethodHook() {
                @Override
                protected void afterHookedMethod(MethodHookParam param) throws Throwable {
                    super.afterHookedMethod(param);

                    Button btn = (Button) param.thisObject;
                    btn.setText("Красный");
                    btn.setTextColor(Color.RED);
                }
            });

        }
}