In this excellent blog post Kathryn Warner refreshes our understanding of Constanza, Duchess of Lancaster, with her usual eye for false myth.
However, one particularly interesting fact arising from the post (in that it relates to the House of York) is that Pedro I, King of Castile, (Constanza's father) was six feet tall with light blond hair!
This will be a shock to those who mistakenly believe that all Spaniards are dark-haired. (They are not and never have been.) It is also an indication that Catherine of Aragon's light colouring may not have come purely from her Lancastrian ancestors, but also from her Spanish ones.
Moving lightly on, we should recall, of course, that Constanza's sister, Isabella, or Isabel, married Edmund of Langley, first Duke of York. So the House of York will have inherited these genes as well. (It seems likely that Langley himself was also blond or auburn-haired and he was almost 6ft tall himself.)
It seems strange then that it is often assumed that Edward IV inherited his (supposed) blond colouring and stature from the Nevilles. Especially as I have yet to see evidence that the Nevilles were particularly tall or particularly blond.