I think I understand the quick solution now. Just writing it here to make sure that I understand correctly:

Let the estimates of my mixture variables X1,X2,X3,X4 be B1,B2,B3,B4 respectively and the std error of each of the estimates be SD1,SD2,SD3,SD4 respectively. Then the 95% CI of my estimates are (B1-2*SD1, B1+2*SD1), (B2-2*SD1, B2+2*SD2) and so on.Then I compute the average of the data as Y/n where n are the number of observations. Now if the inverval (B1-2*SD1,B1+2*SD1) contains the average of the data, that means that X1 is not significant and vice versa. Am I correct?