Can you switch the position of the first co-first author with the second co-first author of an article after it is published? 

Full story: During my PhD, I published two articles, both as the first of the two co-first author. In both articles, the second co-first author is my colleague. My colleague is highly career-driven and ambitious. Although he did not do much work to contribute to either paper (I did 90% of the experiments and analysis and writing, since these are my main projects for my PhD), but he has a good relationship with our supervisor, and managed to convince our supervisor that he did a lot. Our supervisor then spoke to me and insisted that I included him as the second co-first author. I am ok with this, since my name still appears first. 

Now, I have finished my PhD and is going to leave this research group soon. I am worried that my colleague, being career-driven and has a good relationship with our supervisor, may try some means to switch his name on these articles with me, and becomes from the second co-first author to the first co-first author.