In regards to changing defaults, that's often the case. Microsoft do the same thing, possibly worse.
Can you change the default colour palette?
Choose Tools - Options - Charts - Default Colors
We'd have to look into the sorts of changes you mentioned if we were going to stick with 5, so thanks for the suggestions. However, given the graphical glitches and instability, which unfortunately make it borderline unusable on our test system, I don't think we'll be considering a larger scale migration any further until (I assume) some future updates that fix those things have arrived.
The glitches and instability appear to be across the whole suite, BTW. Basic stuff like drawing menus, toolbars and tabs is broken in very obvious ways, all the time. I'm guessing there's some fundamental problem with the routines LibreOffice uses to draw those graphical assets instead of the standard Windows functionality. Either that or there's some horrible conflict with the graphics drivers on the new machine, which is always a possibility but would be surprising at this point given how many other programs do seem to work OK.
Try turning off OpenGL:
You can do this by going to to Tools ▸ Options ▸ LibreOffice ▸ View.
P.S. I'm biased about LibreOffice as I have commit access and I'm working on the code at the moment. I do acknowledge its frustrating when things don't work, and I don't want to deny there are issues preventing you from adopting.
If it's not too much bother, can you file a bug?
I honestly wouldn't know where to start with filing useful bug reports. I'm a software developer myself, so I appreciate the need for useful information and ideally reproducible test cases, but at the moment we're seeing graphical glitches in everything from menu displays to dialogs to the tabs for different sheets, far too many different areas to isolate and investigate each one. It seems more likely that some combination of hardware/software isn't playing nicely on the test system, since presumably if everyone were seeing what we are the LO team would be seeing plenty of feedback already. If you'd like to investigate or try to triage it somehow, I can ask someone to get in touch by mail, and maybe that would lead to something specific enough to be worth putting in a bug report for more detailed investigation?
chris.sherlock79 at gmail.com is my email address, or hop onto #libreoffice-dev on Freenode and ask to speak to chris_wot (that's the IRC channel I hang out on the most frequently).
Try collecting some accounting records in LibreOffice Calc and then finding your accountant uses Excel. Time lost fixing the mess is probably worth more than the cost of MS Office for a single incident. If you need this kind of interoperability more than very occasionally, that alone could be a deal-breaker.
Also, LibreOffice 5 on Windows 7 appears to be a disaster. We installed it for the first time a few weeks ago, on one new PC at work just to try it out, and it's exhibited numerous very obvious graphical glitches, crashes and performance problems so far even just doing basic spreadsheet work. It also seems to have arbitrarily changed a bunch of things from earlier versions, such as the default colours available for colouring or highlighting cells in Calc. Maybe the stability is better on Linux, but even then the changes from LO4 are presumably still the same and just as frustrating.