This is a simple little grid showing all the variations for two of the R G B colors for web use. But most of these colors may not be seen. Remember the limitations of web browsers and the 216 Color Web Safe palette. No graphics were used to create this grid - all the colors are generated by the Hex codes used in the HTML layout.
Notice the change from solid Black at the upper left corner to 100% Red + 100% Blue and 0% Green at the lower right of the grid. Hold your cursor over a color block to see the RGB / Hex color code. The codes are spread apart for inspection and are actually written all together. Ex: #000000