In Photoshop there is a tool that allows you to outline a rectangular shape in an image. You are then able to change the color of what was outlined. The images above shows the original (left) and the modifications I was able to create in Photoshop (right).
Elliptical Marquee Tool
The elliptical marquee tool is used to create an oval or round outline in Photoshop. This can be used to add on effects onto an image and play around with round objects like the cityscape example above.
Magic Wand Tool
The Magic wand tool uses colors to gauge what you want to select. It recognizes what you select and automatically associates other parts that are the same, or close-to the same color. This makes it a user friendly tool that allows for easy selection for cut-and-paste projects.
Quick Selection Tool
The quick selection tool is similar to the magic wand tool because they can both do the same thing. They only differ in how they are used and they way they do it. The quick selection tool not only selects similar tones but similar shapes. This makes it easy to select objects because it captures edges more accurately.
Lasso Tool
The Lasso tool is simple but hard to use accurately. The lasso tool allows for you to make a selection exactly the way you want it because you have to create the outline yourself. If zoom in close enough, you can add, subtract and create your selection accurately.
Polygonal Lasso Tool
You drag and click and it sets a marker, then you can click a again and it sets another marker. These markers mark the end of a line and when you continue it becomes an angle. You continue this until the entire object is selected. This tool is good with selecting polygons because it always makes straight lines.
Magnetic Lasso Tool
Magnetic Lasso tool is like the polygonal lasso tool because they both leave markers. The magnetic lasso tool however automatically leaves markers and is drawn to the shape of an object. The magnetic tool is better for rounded shapes that aren't circular.
Pen Tool
The pen tool is a great easy tool that is very accurate when making selections. It does an excellent job going around edges because it allows you to adjust a line any which way you'd like. You click and drag to create a line and from there you can curve it at several optional points. It is an easy tool that in my opinion is the best tool in Photoshop.