Digital BW, The Print

I am using a Canon S750 and I have discovered the wonderful world 
of black Only printing of photographs;
or so I thought. I was running out of color cartridges too fast and 
found a
newsgroup called  DigitalBlackandWhiteThePrint@yahoogroups.com and 
have
learned a lot. I read many of the messages and logged on to many 
websites
mentioned in them. As a result, I discovered
http://www.cjcom.net/digiprnarts.htm which dealt with using only 
black ink
for printing the images. It is a learning curve, I admit, but I 
buckled down
and worked with it over the course of a few weeks till I became 
familiar
with the technique. I started print images and noticed almost all of 
them
has some color cast to them, but I chalked it up to the ink and paper
combination. Today I got a screen message from my printer that my 
Cyan and
Magenta inks were running low. I wondered how this could be possible 
because
I was using only black ink; or so I thought. Going back over 
everything
carefully, I reexamined a vital printer setting I thought would not 
be
necessary to set initially. One toggle for color management 
was "Auto" and
"Manual" and I had it toggled as "Auto". Changing this to Manual did 
not
seem to make any difference in the color cast of the prints, and now 
I am
running out of color inks. If I take them out, the printer won't 
print
anything on the paper at all, or if I tape over the ink sensor it 
won't
print at all. Has anyone else had this same problem and solved it? 
If so,
please send me email directly jeades1@... or you can post it 
on this
newsgroup so all can benefit from your knowledge. Thanks in advance 
for any
and all help you can give me with this dilemma.