Some of the color controls are also available on the Active Variable Controls toolbar.
The Color Scale tab controls many aspects of the color map you will be using, such as the color space, range, etc...
The color bar at the top of the window shows your current color map. All the nodes on the color bar have a specific color (associated with a particular scalar value) that can be modified by simply clicking each one of them. You can drag the node to change its scalar value and transparency. Click on this node again to bring up the Select Color window in which you can choose a basic color or customize your own. You can add colors to your color map by clicking anywhere on the color bar, which will add a node. When a node is selected, it becomes slightly larger than all others. While selected, the node can be deleted using the backspace or delete key. You can use this method to customize your own color maps from any preset.
You can also choose from existing color maps by clicking on Choose Preset. This brings up a window containing existing color maps and ones that have been previously imported. From the Preset Color Scales window, select a color map and click OK to apply it to the selected dataset.
Another alternative is to import or export Color Map Files (*.xml) from the Preset Color Scales window. You can import custom made color maps or export them to other applications.
The Scalar Value text box tells you the value of the selected node. This text box is grayed out when an edge node is selected. You can change the value of a node (except for the two at the edges) by typing a value over the existing one. This moves the node along the color bar to the specified value without changing it's color. You can also drag a node manually to change it's value.
Usually, the Opacity and Scale options are grayed out. Only when a dataset is represented as a volume (not geometry) can you modify the opacity and scale of the color map. When the opacity is 1, the color is completely opaque and the node is at the top of the color bar. When the opacity is between zero and one, the color ranges from invisible to lightly transparent and the node is placed lower.
The Color Space drop-down menu lets you choose from various color spaces such as RGB, HSV, Wrapped HSV, CIELAB, and Diverging. Choose the one you would like to use for your color map.
Checking the Use Logarithmic Scale checkbox sets the scale to logarithmic rather than linear.
You can set your color map to Automatically Rescale to Fit Data Range which matches the data array range to the color map range automatically. The minimum and maximum values displayed under this check box option correspond to the color map range and not the necessarily the data range. To manually rescale, uncheck the Automatically Rescale to Fit Data Range option, click Rescale Range and enter values. Click on Rescale to Data Range to rescale the color map to the data array range.
The last section of the Color Scale tab allows the choice between using discrete colors and continuous colors. A discrete color map uses a fixed number of colors and maps the range of scalar values to those colors. Check the option Use Discrete Colors and set the number of colors with the Resolution slider. To use continuous colors, uncheck the checkbox.
Use the Make Default button at the bottom to set which color map and settings you want applied by default.
To show the Color Legend in the active render window, check the Show Color Legend option. This shows the color map and it's range as a stationary object in the 3D view.
You can change the font style and label properties of the color legend in this panel.
The format of the labels can be set automatically by checking off Automatic Label Format or manually by unchecking it and modifying the Label Format using printf syntax.
The Label Format's default syntax (%-#6.3g) can be read as follows:
Number of Labels allows the user to change the number of labels in the color legend and the Aspect Ratio controls the width of the legend.
 Active Variable Controls Toolbar
The Active Variable Controls toolbar can be turned on from the View menu.