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.Which one you usedepends on the requirements of your software.DecimalMost image editing software displays the RGB value of a color in decimalvalues, ranging from 0 to 255.A color s decimal RGB value might be 51-51-255, meaning the red value is 51, the green value is 51, and the blue value is255.Note that these numbers specify one of 256 possible values for eachchannel; they are not percentage values.Web-safe colors are multiples of 51.HexadecimalHTML and many programming languages require that RGB numbers be speci-fied in the hexadecimal numbering system.Hexadecimal is a base-16 systemColor on the Web 31Web Design in a Nutshell, eMatter EditionCopyright © 2000 O Reilly & Associates, Inc.All rights reserved. Color on the Webthat requires only six characters to describe an RGB color.The hexadecimalequivalent of 51-51-255 is 3333FF.PercentageThe Apple Color Picker specifies colors in percentages, not absolute RGBdecimal values.For Macintosh programs that rely on the Apple Color Picker(such as Claris HomePage and Adobe PageMill), you ll need to be able toconvert percentage values to true decimal values.The percentage value equiv-alent of 51-51-255 is 20%-20%-100%.Table 3-2 shows the decimal, hexadecimal, and percentage values for each of thesix component values in the Web Palette.Table 3-2: Numerical Values for Web Palette ColorsDecimal Hexadecimal Percentage0 (darkest) 00 0%51 33 20%102 66 40%153 99 60%204 CC 80%255 (lightest) FF 100%Reducing to the Web PaletteColors on a web page are forced to adapt to the browser s Web Palette.The onlyway to ensure that all users will see your colors as you intend them is to use web-safe colors when you design the page.(See Designing with the Web Palette inthis chapter.)Colors in ImagesBrowsers attempt to approximate the colors in an image by dithering, mixingpixels of similar colors available in the palette.For photographic images, theeffects of dithering are usually not detrimental (and in some cases may bebeneficial).However, in areas of flat color (such as in a logo or line-art illus-tration), the random dot pattern caused by dithering may be undesirable.Chapter 17, Designing Graphics with the Web Palette, discusses techniquesand tools for applying the palette to graphics during the design and produc-tion process.Colors in the HTML documentColors specified in the HTML document, such as background and text colors,will usually be replaced by the nearest available Web Palette color (InternetExplorer may dither background colors).This effect is called color shiftingand it can result in a large discrepancy between how a color (as defined by itsRGB values) is rendered on a 24-bit display versus an 8-bit display.Designing with the Web PaletteWhile the Web Palette can lead to unpredictable and undesirable effects such asdithering or color shifting on 8-bit monitors, you can also use it to your advan-32 Chapter 3 Web Design Principles for Print DesignersWeb Design in a Nutshell, eMatter EditionCopyright © 2000 O Reilly & Associates, Inc.All rights reserved. Color on the Webtage.Because you know exactly which colors will render accurately on Macs andPCs, you can use these colors exclusively when designing your graphics andHTML pages and beat the browser to the task.It requires a little extra effort, butthe advantage is that you ll be able to predict what the pages will look like for allusers.Using web-safe colors in graphics production is discussed in Chapter 17.If you choose to add color to the background and text on your web pages,chances are you ll need to do some experimenting with color to get the combina-tions just right.There are a number of tools and options for selecting web-safecolors and incorporating them into your designs.Web authoring toolsMany WYSIWYG (What You See Is What You Get) web authoring tools (includingMacromedia s Dreamweaver, GoLive Cyberstudio, and Claris HomePage 3.0), allowyou to choose from swatches of web-safe colors when applying color to text andbackgrounds
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