Re: colour mode problem
The way I tackle this problem is to use a known colour palette. What I mean by that is to make up some form of colour wheel or block colours with stated RGB & CMYK values then get that printed by your printer which maybe digital or off-set then you have a visual reference. This means that surprises are kept very low as you can take tints of these colours and so long as you don't stray that far from the values no big surprises. This is a bit like your pantone book without the Pantone values staying either in RGB or going CMYK colour profiles as Mike states.
It's the darker colours that cause the most surprises! especially dark Reds & Greens. Using this limited colour palette may make your drawings look a bit the same but hell I can stand that.
Design is thinking made visual.