shade levels

[Rajesh J]

hello,
can anybody give the syntax in GrADS to make desired shading for different
levels? when i tried like
'set rgb 20   20 40 60'
.......
........

colndx='-18 -16 -14.....'
colevs=' 92  91  90.....'

'set gxout shaded'
'set clevs 'colndx
'set ccols 'colevs
'd x'

it doesnt display any thing. can anybody point what could be wrong? or is
there any other way to do it? please attend.
thank you,