I did a 2 year long research study in undergrad with a highly profound professor and her PhD student. I worked very closely with the PhD student and I know he would have a lot of good things to say about me in a letter of rec. The professor oversaw my work but didn't work as closely with me, however she has a lot of notoriety in her field. I'm not sure if she would write as good of a letter as the PhD student but she has a ton of experience and success.

I have 2 questions:

Is it acceptable to get 2 letters of rec from the same research project? (I can ask other professors as well but I know my research professor and her PhD student the best)

If I only use 1 letter of rec from this project, which one should I go with?

I am currently putting together my resume for admissions and I am pretty much done with all of the content, however, the format of my resume is very boring black/white. Do you think this will have a significant impact on admissions or does resume format not really matter for these kinds of applications?