Thank you macropod.

Your answer is very clear but I have a couple of doubts/concerns:

1) You say that every time that the field updates the image revert to the original colors. Is it the same for the size as it is apparently happening in my case?

2) About using Tables for the images. It might be a bit late to change that in my document but maybe I have no choice..... The only thing is that I also have Tables with equations and with the caption "Table" instead of "Figure". Is there any risk on having some tables with images and other tables with different data and different types of captions for every table?

Thanks.