Painting watercolor over a drawing.

Maybe this has been covered before, in which case I apologize.  I'd never be able to search for it with the new forum. I like drawing most, adding color is really a sideline for me.  (Although perversely I like bright color in paintings).  What I want to do is put washes of watercolor over a drawing.  The problem is the wash picks up some of the graphite, dirties the color and degrades the drawing.  I tried it a while back...here it is.... This started as a full bore drawing, ie, all the shadows were penciled in with a variety of pencils from HB to 6B.  I tried gently laying on thin washes of watercolor.  It got dirtier and dirtier, so I laid on more watercolor mixed with a little white gouache.  This certainly 'improved' things, but it wasn't what I was after.  You'd never guess this started as a fully worked drawing.  I had another go, fixing the drawing with some ancient fixative that I'd had for a while.  It darkened the image slightly, and didn't accept the watercolor very well...I suppose I was expecting that. I've just had another go, using a drawing in one of my sketchbooks.  I was hoping to retain the 'drawn' look, but add some color.   Prior to doing this I'd looked up fixatives, but all they talk about is 'fixing' the drawing...no mention of whether you can paint over it.  But I had a go anyway, with no fixative...here's the original drawing, and the 'color' version.  It's almost what I'm after but not quite.  Has anyone tried this?  Would a modern fixative help?  Any ideas?

Thanks Alan.  I am using Lumograph pencils, they were recommended on the forum some time back and I've been using them since.  I'm a little surprised the colored drawing came out so well...I was using 6b (maybe even 8B here and there).  But if you look at the seated figure's face you'll see the shadows aren't so dark as the drawing.  (I know contrast etc is at play when talking about B&W and color.)  Also the scribbled effect on his collar, is much paler.  All to be expected I suppose, when 'watering' something down.  I've looked up the solid graphite sticks...not something I'd have thought of, but well worth a try. It's the 'pencil drawn' look I'm after, Robert.  I use ink and watercolor, plus a little gouache, a lot.  I guess I'm after a transparent color that shows the drawing underneath...in the first pic I showed I've lost that.  It's pretty much there in the second pic, just a bit wishy-washy in places.  Maybe I'm asking too much from the materials, and a lot of touching up after applying the watercolor is the only solution. The watercolor pencil idea is good, I could use that as a normal pencil.  Maybe applying water to that drawing would 'seal' it slightly.  I'll try that tomorrow if I get the chance.  I'll post the result here, whatever happens. Thanks to you both for your advice.

Up with the larks this morning, so I tried drawing with an ivory black water-soluble colored pencil.  First I drew the outline with a strong line, added a little shading here and there (using the pencil more gently), then I used a brush and clean water over all the lines and blending the shadow areas.  This is a pleasant technique, you pick up enough pigment to virtually draw with the brush.  When it was dry I applied some very wet thin washes.  This was done quickly and lightly, the brush did pick up a little of the black drawing, but not enough to worry about.  The colored version required no titivating after applying the washes. It gives a slightly different look to my pen and watercolor stuff...which appeals to me.  This quick sketch has me believing it's worth trying with more care and on better paper. Thanks for the advice.   I didn't think I could 'fix' the drawing and then apply watercolor...but you never know, it's worth asking.  (I will try the graphite sticks later).