I have brown eggs and couldn't see anything until last night (day 5) when others see stuff at day 3, so I think it just depends on how dark your eggs are.
Here is my egg at day 5.

Here is my egg at day 5.
Well today is day 5. I will candle on Saturday. I attempted to candle last night but my barnevelder eggs are too dark to see any veins. Is it normal to miss them at this age? Will I be able to see anything a little later?