His friend might have some beautiful, ancient, golden Bald Cypress and he was told it was poplar by somebody who knows how to sound more better talking about things but doesn't actually know more better about the things he is talking about. Bald cypress can have a beautiful golden color not ugly like golden oak of the 80's and 90's, but a definite warm brown to gold finish. So now the guy you are working for wants some ancient old growth Bald Cypress but he's telling you he want's poplar because his friend that doesn't know what he has told him it was poplar stained with golden oak. I was born in New Orleans. Things like this happen all the time in Louisiana. It's how things are done. We tell stories. Kid I went to school with had a neighbor who had a piece of the cross that Jesus was crucified on. The actual Jesus crucified by Pontius Pilate. Kid said she touched the crucifix wood and it burned her. I always hoped that poor kid didn't touch a piece of creosote or penta soaked foundation piling (sort of like telephone poles we drive into the ground to keep our houses from sinking in the mud/clay we call gumbo).
Long story short, show him a piece of poplar that has green/brown streaks in it and a piece that's damn near white and featureless. Make sure his idea of poplar matches what poplar actually is.
I have dyed poplar with Transtint dye and then stained with General Finishes gel stain (oil based). I've made jet black accents this way and had a few interesting results that made poplar look good in the small items I made with it.
I needed some easy to work wood from Home Depot, and poplar was what I came up with. I've been happy with it for several small projects for telescope parts, tool handles, gun stock spacers, and table saw handwheels (don't ask, but it worked) and such.
I don't think I would make a bed out of it.