The OEM HID bulbs are indeed 4300K but the colour they give of is also influenced by the reflector design and mirror colouration.
Aftermarket replacement at 4300K will look off white towards yellow. To get the same look, you have to go down the 6000K temp colour range route. This gives a bright white with the signature blue tint.
PS Aftermarket HID bulbs in cars not originally specified to have them fitted, i.e. those without auto-adjustment on the beam height (manual adjustment by the dashboard knob doesn't count), and headlight washers are illegal in the UK and can result in non-payment of insurance claims if they are found on a UK car involved in an accident. Although many people use aftermarket HID kits on H7 and other bulbed cars, they are illegal. However they may well pass, and should pass, an MoT as the test looks for beam pattern, not bulb design or output.