"id" % 2 = 0

"id" % 2 != 0

from PyQt4.QtGui import QColor

layer = iface.activeLayer()
idx = layer.fieldNameIndex('id')
style_dict = {}

for feat in layer.getFeatures():
    if feat[idx] % 2 == 0:
        style_dict[(feat[idx])] = ('#ff0000', str(feat[idx]))
    else:
        style_dict[(feat[idx])] = ('#46add4', str(feat[idx]))

categories = []
for name, (color, label) in style_dict.items():
    symbol = QgsSymbolV2.defaultSymbol(layer.geometryType())
    symbol.setColor(QColor(color))
    category = QgsRendererCategoryV2(name, symbol, label)
    categories.append(category)

# field name
field = 'id'
renderer = QgsCategorizedSymbolRendererV2(field, categories)
layer.setRendererV2(renderer)
layer.triggerRepaint()