That sounds really odd that updating a logo file would take days to change. What web host are you using?
I am with Bluehost. They have installed varnish cache, but do not give end users access, so clearing it requires contacting support. Or wait for it to clear, which happens every 30 days! They are "working on" a way to give end users the ability to clear the cache, but until then...
Thanks for the location - I was looking in css files. Got it going now.