Is it possible to edit a video in Pleasantville effect with
If not, what software does?
https://www.google.com/#q=Pleasantville+video+effect&undefined=undefined indicates that is for Apple's Final Cut
You might try asking the effect's author if they have a version for Premiere Elements
Much much much much easier in After Effects (where it was likely created).
Very difficult in Premiere Elements (if you're talking about have some objects or people in a video be in color while the rest are in black & white).
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