How do I mask or correct a lightbox so that I can remove the X in the corner?

Hi, Storyline friends.

Thanks for taking the time to help in the midst of everything going on!

I have a series of lightbox yellow light box slides that are accessed when learners click lightbulbs. Because they are lightbox slides, each has an X in the corner but I already have another X (a blue one) that I want learners to use instead as it will take them back to the main slide. (The lightbox X will just take them back to a layer, which is not where I want learners to go).

I am hoping there is a simple fix that will allow me to get rid of the X in the lightbox corner so that learners will use the blue X instead. I don't know how to build this or do this and am hoping I don't have to rebuild the whole thing to achieve what I am hoping to. There may be a simple trick like masking but I don't know how to do that. 

Can someone pls take a look at this file? I would appreciate if you could fix this for me and/or give a detailed explanation on how I can do that.

Thank you so much!!