Below are some resources I use to create apps. There's nothing "magical" about it nor complex. These resources will help you get started building your app quickly.
INTERNET BASED RESOURCES
Google Chrome-Although the app building software is compatible with any web browser, Google Chrome is the browser that I choose to utilize.
The SnagIt extension is a Google Chrome extension. Record a portion or entire screen and do a direct upload to YouTube as well. Currently, it's not possible to download it. A similar functioning software is ShareX.
Dropbox-This is perhaps one of the most well known cloud storage services. This will allow you to store and share all types of files for yourself and for those whom you work with once they get permission. Get started here.
App Building
When it comes to building an actual app, you can use the Mobile App Maker Pro App Building Guide to help assist you when you quickly build a mobile app for your small business or for others. I'll show you how to connect various social media elements as well. Here's some things that you can use on the internet to help you build an app in very short order.
If you are trying to get the color scheme:
Image Color Picker: Upload your image and get the hex color code
Background Image Generator: Create color coded backgrounds.
Website Color Combos: Grab the hex code of an entire website.