how would you build a flaming blade?
frost blade?
electro blade? 
There is a CrIg spell, Blade of Virulent Flame, that does the flaming blade... you'd just invest it into an item.
A "frost blade" would be PrIg.
A "lightning blade" would probably be CrAu... but unlike fire, lightning doesn't really tend to hang around in one place much so it would be a heck of a spell to hold a bolt of lightning to a blade. 
Blade of the Virulent Flame, CrIg lvl 15, page 140.
A PeIg variant of the above.
You're looking at a level 35 CrAu at a minimum, but first, you need to forget modern notions about electricity, which lightning is not, in Mythic Europe.
Abe ,
You still working from your pdf of 4th Edition?
Probably a good idea to let people know which edition you have.
yes,I have 4th ed.
Then you can find the Blade Of Virulent Flame on page 135 (you should have found it when reading the Creo Ignem section, which was the obvious place to look).
The ice variant would probably be similar.
Unless I am mistaken, the lightning variant would be Creo Auram level 35 (exercise - figure out how I reach this number), most likely with a Rego requisite, since it is not in the nature of lightning to "stay put" on a blade, unlike fire (which clings to the things it burns) or ice (which is solid).
Lets revive a few of the oldest Abe threads for any newer members who may want to contribute.