activity_main.xmlMainActivity.java
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.codinginflow.spannablestringexample.MainActivity">

    <TextView
        android:id="@+id/text_view"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="I want THIS and THIS to be colored"
        android:textSize="20sp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</android.support.constraint.ConstraintLayout>
package com.codinginflow.spannablestringexample;

import android.graphics.Color;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.text.SpannableString;
import android.text.SpannableStringBuilder;
import android.text.Spanned;
import android.text.style.BackgroundColorSpan;
import android.text.style.ForegroundColorSpan;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        TextView textView = findViewById(R.id.text_view);

        String text = "I want THIS and THIS to be colored";

        SpannableString ss = new SpannableString(text);
        SpannableStringBuilder ssb = new SpannableStringBuilder(text);

        ForegroundColorSpan fcsRed = new ForegroundColorSpan(Color.RED);
        ForegroundColorSpan fcsGreen = new ForegroundColorSpan(Color.GREEN);
        BackgroundColorSpan bcsYellow = new BackgroundColorSpan(Color.YELLOW);

        ssb.setSpan(fcsRed, 7, 11, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
        ssb.setSpan(fcsGreen, 16, 20, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
        ssb.setSpan(bcsYellow, 27, 34, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);

        ssb.append(" and this to be appended");

        textView.setText(ssb);
    }
}