findng array[3] in array[3,n]

["tbowers" <tbowers(at)nrlssc.navy.mil>]

If I have

a=[ $
 [0,1,2], $
 [3,4,5], $
 [6,7,8]]

b=[3,4,5]

how do I find where in a is the row vector b? The answer should
be 1, the 2nd row of a. I've tried many
permutations of where(), but I just don't get it. The only way I
can get an answer is to loop through the rows till i find a match.
What I'm really tryin' to do is to find a color in a color table,
e.g. load RAINBOW color table, (loadct,13) then identify
where a color is. For the color that's listed 6th in the color table
(an almost black) that'd be the 5th row index. Like:

loadct, 13
tvlct, r,g,b,/get
colorTable = transpose([[r],[g],[b]])  ;//a [3, 256] array
colorALMOSTBLACK=[22,0,9]
indexALMOSTBLACK=where(colorTable eq colorALMOSTBLACK)

What I want is the answer 5 because if you print the 1st 6 rows
of colortable you get:
print, colorTable[*,0:5]
   0   0   0
   4   0   3
   9   0   7
  13   0  10
  18   0  14
  22   0  19

I'm looking for that 6th row which is [22,0,9], my search array.

I've tried alot of different stuff, but i just don't get it
IDL> print, where(colorTable eq colorALMOSTBLACK)
           1
IDL> print, where(colorTable[*,0:*] eq colorALMOSTBLACK)
           1
IDL> print, where(colorTable[*,0:*] eq colorALMOSTBLACK[0:*])
           1
etc., etc., etc....

So, does anyone know see an elegant solution to this problem??

tia,
tbowers