Rectangle Tool method: Draw rectangle and change its fill color. Document Setup method: Use Simulate Colored Paper option. Layers Panel method: Create new layer and fill with desired color. Existing file method: Export to Web (Legacy) and change background
Command/Control + Z is the quickest way to undo changes. Shift + Control/Command + Z allows redoing previous undo. Toggle Last State (Control/Command + Alt/Option + Z) shows last change
Image Rotation menu offers quick portrait to landscape transformations. Crop Tool allows manual rotation without adding empty space. Smart Objects enable multiple rotations without losing quality
Rotate entire image using Image > Image Rotation. Select object with Quick Select tool. Rotate selected object via Edit > Transform > Rotate
Open Photoshop with blue square "Ps" in the middle. Click File menu at top of screen. Select Open option from dropdown menu. Browse and select desired image. Click Open to insert image as new layer
Select image in Layers panel and open Adjustments menu. Use Invert tool or CTRL + I shortcut. Invert entire image or specific selection using Levels adjustment