Some Alder has a pinkish cast, but if you select well, Alder and any species of Maple (at least the sapwood) will be a light blond. The annular rings in Maple are a bit more distinct than Alder.
An Alder body will be a lot lighter in weight than Hard (Rock, Sugar) Maple, but just a little lighter than most Soft Maples. Hard maple is a lot harder to sand than Alder. Hard Maple has a higher surface sheen than Alder. That is, if you take a piece of each and sand them to 600, the Hard Maple will look like gloss, and the Alder will look more satin. That will also be true if you apply a gloss finish - the Maple (especially Hard Maple) will glow more.
I've never built an electric, but I did a little work for a luthier that included refinishing bodies. Alder bodies were common - I never saw one that was solid Hard Maple.
HTH,
Dennis
p.s. Here's some info if you want to compare properties: Tech Sheets North American Hardwoods