1. I like myPantone, although it may be more helpful for computer work/graphics. It lifts the color palette from an image and gives you the recipe to match (RGB, etc) in photoshop, etc.
2. Sun Surveyor is good for plotting sun/shade in smaller scale work. You can look through the camera on your phone to see where the sun will be at different times of year relative to what you see on your camera/screen.
3. In the SE US, Dirr’s Woody Plants is available as an app. Dirr is my plant reference of choice, and it’s handy to have it convenient. (The book is huge and heavy!)
I wish they would make a Time Savers/Standards app or audio book to help me study for the LARE. 🙂