When two colors are placed next to each other or are interspersed, they cause a visual reaction where the two colors appear as their opposite color. This effect is known as simultaneous contrast.
For example, if you were to take a bunch of red circles and place them next to a bunch of blue circles, where these colors touched the blue would appear greener and the red would appear more orange.
Putting it merely and scientifically speaking, this phenomenon occurs when light enters intricate, specific color receptors in our eyes, causing those receptors to become stimulated, overloaded and fatigued, which in turn causes these colors to look like other colors.
Webexhibits.org,. "Simultaneous Contrast". N. p., 2016. Web. 15 Jan. 2016.
Illusion of Depth and How to Achieve It
Transparency, occlusion, focus, lighting, shading, shadows, color, size and scale, etc., are all possible visual cue that tell our brains that there is depth in an image.
Bright colors stand out in an image while cooler darker colors seem to visually recede.
The visual effect of transparency which is a form of occlusion sends the cue to our brain that one object is in front of another, thus providing the illusion of depth.
The occlusion of two object has the same but stronger effect. When an object is completely obscured by another object in an image our mind sees the object that is being obscured as being behind the other object even if it is a two-dimensional surface.
Depth of field can easily be created by making a portion of an image appear sharp and the surrounding image blurry. The closer an object is in real life the more we are able to focus on that object, whereas the farther away an object is the more blurry it becomes.
Bradley, Steven. "11 Ways To Add Depth To A Design - Vanseo Design". Vanseo Design. N. p., 2012. Web. 15 Jan. 2016.
Analogous Color Scheme
An analogous color scheme is made when you take three or more hues that are positioned in a row on the color wheel and present them together. For example, Red, Red-orange, Orange, or Blue, Blue-green, Green.
RGB and CMYK
RGB stands for Red, Green, and Blue. These are the primary colors of light that are used by computer monitors and various other electronics. When each of these colors is projected together, they make white. Black, in this instance, is the absence of color.
CMYK stands for Cyan, Magenta, Yellow, and Black, which are the primary (ink) pigments used in printing. The color white, in this case, is the absence of pigment/color.
If you are to convert a document from an RGB color scheme to CMYK the colors may change becoming darker or duller. The same goes for when you are printing an RGB image on a CMYK printer the colors may show up darker or duller.
In general RGB colors tend to be more vivid that CMYK and many RGB colors cannot be duplicated in CMYK.
Web colors are colors used in web pages. These colors are expressed using what is known as a hexadecimal triplet, or six-digit three-byte number, or an RGB triplet format, or three numbers in a hexadecimal format. For example, my favorite hue is turquoise (surf green) which is represented as 40 E0 D0 in hex code, or 64 224 208 in decimal code format within a webpages source code.
The color profile within Photoshop that is used by most web browsers when displaying images on the web is known as sRGB. If you are making images for a web page and not for print, you will want to convert your files to the sRGB color profile in order to have them appear correctly when adding them to a webpage.