Because we're looking at European bikes I'd say....

Blue: PS10 because it has the 49D crankset. It should have a 3-tubes Reynolds frame with Reynolds fork blades. A PX10 would have Reynolds sticker that says something about the stays being 531 as well as having a Stronglight 105 crank. Regardless, its a nice bike.

Silver: In the U.S. it would be a UO10 as it has alloy wheels, an alloy crank and downtube shift levers. In Europe its probably a PA10.

They fall into the '75-'78 date range. You can further narrow down the year by checking dates codes: http://cyclespeugeot.com/SerialNumbers.html