Line symbology differing radically between ArcMap MXD file and web-rendering in ArcGIS Map Viewer or Web AppBuilder

I am building and publishing a map in ArcGIS ArcMap with one layer and two polygon areas symbolised by differing colours of diagonal line symbology: no matter what I have tried as the base Referenced Style, eg '10% simple hatch', 'biohazard overlay' and other predefined diagonal styles, on which I've then edited color, line thickness, outline, separation etc, I always end up with a map web view (ArcGIS Map Viewer, Web AppBuilder) with a basic hashed, greyed-out diagonal where my chosen color doesn't render: the only difference I can see between, eg, IE11 and Chrome is that the rendered line style is not hashed / broken in the latter. But it is still black rather than my chosen color, and the selected thickness is ignored. Is there a best-practice regarding use of custom lined polygon styles ?