Hey Joe. . .
I just installed 5.3.3.2 on my Ubuntu 16.04 laptop. I had 5.2.x installed but I realized that I had forgotten to install the newest version when I did on a different laptop [17 inch]. That different one had a fresh install of both Ubuntu 16.04 and Windows 10 Home.
Here is what I tried.
I pasted some text into Writer. I selected a large block of text and then clicked on the font color [red was the last one used]. I had no problems with it changing the text to red. I tried changing colors and no issues there.
Since I do not have 17.04 installed, I could not test it using that OS.
Just for reference - what version of LibreOffice was installed with Ubuntu 17.04? I tend to installed the latest version of LO after I upgrade to a newer OS. Of course, I tend to forget to upgrade LO after that. 3 strokes can do that.