Most (but not all) EGA cards that suit the 5155 do not have a composite video output. That is a problem fitting it, because the composite output is needed to drive the internal amber CRT monitor in the 5155. But a "feature adapter" can be made to get around this and also get very clear video graphics on the amber monitor, because the Chroma sub-carrier can be omitted (it causes patterning by beating with the high frequency luminance components of the video).
This article might be of interest to those wanting to fit an EGA card to the 5155:
http://worldphaco.com/uploads/FITTING_A ... M_5155.pdf