There is a problem of color display of Geometric Primitives in part workbench.
As the first figure show, a line and a circle is built using the part workbench. Then save the file after setting the Line Color.
The color of the line and circle turns into black when opening the file again as shown in the second figure. But the property value of Line Color remain unchanged.
revolOS: Windows 8
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.17.7447 (Git)
Build type: Release
Branch: master
Hash: 898bd8bb4cbe2c9b26aa6c1f7362e48752a3e4de
Python version: 2.7.8
Qt version: 4.8.6
Coin version: 4.0.0a
OCC version: 6.8.0.oce-0.17