Citing ideas but extending information Imagine the following situation: Mr. Expert writes that it is important to have A,B &amp; C. Dr. Smart writes it is important to have A, Y, Z. As both are using the arguments to lead to different topics, their list is not exhaustive and {A,B,C,Y,Z} do not contradict. 

I think all points are important, but I would also like to add that A may be red or blue. Hence I think:

Red and blue A, B, C, Y and Z are important.

But how do I cite them correctly?

Red and blue A, B, C, Y and Z are important [Mr. Expert; Dr. Smart].

This is the only form that doesn't make the sentence contain more citations than actual words. Is this a bad citation style, e.g. might Mr. Expert complain that he never said A should be red or blue or that he thinks Z is completely irrelevant? Or am I just noting that some ideas might be copied from one (or maybe multiple) listed sources?
It seems to me you should simply expand the text to provide the background that "Expert (cite year) has shown that A,B &amp; C are important and Smart (cite year) has shown that A, Y, and Z are important. Based on circumstances I postulate that also Red and Blue A are important along with B, C, X, Y, and Z". I hope you get the point? In other words describe the findings of Expert and Smart and then add your own "hypothesis" or ideaand make it clear that (a) it is your idea and (b) on what you base the idea. It is not clear fom th equestion whether it is a hypothesis to be tested or a result of your own research. Depending on which the way you present things will be slightly different, of course.