epub converter: fix color to all in hex 3

src/css_reader.py

@@ -95,7 +95,13 @@ to suit livecarta style convention.
 
 def get_bg_color(x):
     color = str2hex(x)
-    color = color if str2hex(x) not in ['#ffffff', '#fff'] else ''
+    color = color if color not in ['#ffffff', '#fff'] else ''
+    return color
+
+
+def get_text_color(x):
+    color = str2hex(x)
+    color = color if color not in ['#000000', '#000'] else ''
     return color
 
 
@@ -106,7 +112,7 @@ LIVECARTA_STYLE_ATTRS_MAPPING = {
     'font': lambda x: '',
     'font-family': lambda x: LawCartaConfig.font_correspondence_table.get(x.capitalize()),
     'font-size': convert_font_size,
-    'color': str2hex,
+    'color': get_text_color,
     'background-color': get_bg_color,
     'background': get_bg_color,
     'border-top-width': lambda x: x if x != '0' else '',