Improve your posts with recommended templates.
Canva is an online photo editor that has templates for various social media platforms, emails and much more. Canva also has a catalog of free and premium images that you can choose from. If you have your brand colors (green and blue) then you can have a preset of them so you do not have to guess or remember that specific shade of your colors.
I created the featured image in the canva app on my iPhone. This is more convenient for making Instagram photos. Although the website version allows for more precision. Certain features require you to pay for the pro version but you will have a lot of resources available on the free version.