Can I ask which theme you're using? Each theme is different and if you're using a free Shopify developed theme, your best next step could be contacting an advisor on our support team here. If it is a paid third party theme, it could be worth contacting the developer directly to see if this is an error on their end since the images shouldn't be cut off on desktop.
It's difficult to know what's happening with your store without seeing it directly. If you could share a link and screenshot of exactly what you mean, that would be great.
With regards to the colour change, it is definitley possible to edit the color's of certain aspects of sections but it would depend for where exactly. It might involve some editing to the code and it could be worth asking either our theme support team or the developer once you're in contact with them, but it should be possible!
Please send your site and if your site is password protected, please send me the password.
I will check it for you.