Graphic question

[Peng Du]

Hello all,

Is there anyway I can represent the value with level of darkness? I
mean if I have time as X-axis and the items I monitor on the Y-axis,
can I have a horizontal stripe and indicate the high/low of the value
at specific time with how dark the colour of the stripe is at the
corresponding position? Something looks like this one:
http://spie.org/Images/Graphics/Newsroom/Imported/0951/0951_fig3.jpg ,
but it does not have to be colourful.

Thanks a lot.

Regards,

Peng