K, I'll try to make this brief, cuz i tend to go 
on and on.

monochromatic: consisting of any tints or shades 
associated with one hue(color). So your ayeka cel 
is truely monochromatic. And unfortunatly, this 
all white cel you speak about is not technically 
monochromatic, because it lacks color. White is 
not a color, it is a shade. ;) (black is not a 
color either, it is also a shade). 

Now your question refers to the "limits" of the 
colors. If your ayeka cel had greens and purples 
in it, then it would have an "analogous" color 
scheme. An analogous color scheme is when the 
colors used are next to eachother on the color 
wheel (they share a primary color in common. For 
example, red orange and yellow.)

If you have any other questions about color, you 
can consult this very very helpful online art 
dictionary:

www.artlex.com

ttyl :)
/Tara