I installed plantuml v.1.2017.13 on tomcat 7 successfully,
but I found differences comparing against the online plantuml web page, which is same version:
The color is white including background and input area.
No "Switch layout" button, this is very useful function!
The input area has line number, it's also a great feature. I like it!
I don't know why and hope "Switch layout" come back at least.
[My web page]
[Online plantuml web page]