The vectors in the Vector plot can be colored by the magnitude of the vector variable or they can be colored using a constant color. Choose the coloring method by clicking on either the Magnitude radio button or the Constant color button. When vectors are colored by a constant color, you can change the color by clicking on the color button next to the Constant radio button and choosing a new color from the Popup color menu. When vectors are colored by magnitude, the color is determined by one of VisIt's color tables, which can be chosen from the Color table button next to the Magnitude radio button.
If you choose to color the vectors by their magnitudes, you have the option of also specifying minimum and maximum values to aid in the mapping of vector magnitude to color. The options that are used to aid coloring are collectively known as limits. Limits can apply to all vectors that exist in the dataset or just the vectors that have been drawn by the Vector plot. To specify which, choose the appropriate option from the Limits combo box. When you specify a minimum value all vectors with magnitudes less than the minimum value are colored using the color at the bottom of the color table. When you specify a maximum value all vectors with magnitudes larger than the maximum value are colored using the color at the top of the color table. To provide a minimum value, check the Min check box and type a new minimum value into the Min text field. To provide a maximum value, check the Max check box and type a new maximum value into the Max text field.