Flash is rather blue and tungsten lights used in households are orange, so a gel is necessary. Many of the gels are matched to studio tungsten hotlights, which are higher in temperture than the typical household lights. Because of this, it may be difficult to find the perfect match, there will probably be some difference between the subject lit by the gel covered flash and the ambient light background, but it will be very minor.
RP, 60D, RF 24-105mm f/4-7.1 IS, RF 35mm f/1.8 IS, RF 50mm f/1.8, EF-S 10-22mm f/3.5-4.5, EF-S 18-135mm 3.5-5.6 IS, EF-S 55-250mm f/4-5.6 IS, Tamron 17-50mm f/2.8, EF 28mm f/1.8, EF 50mm f/1.8, EF-S 60mm f/2.8 macro, EF 85mm f/1.8, El-100, 430ex, 220ex, Alien Bee B400 (2), Alien Bee B800 (2)