If I'm being honest, there wasn't really a whole lot of research necessary to be able to make this particular ballcap. All I really had t go on (and all I really needed) was this photo of pitcher Jerry Casale. The photo is stamped "June 10 1954" on the back, which was the only year Casale played for the Senators.
With any black and white photo, determining colors is always the biggest pain in the ass. One thing that it very clear to me from this image though, is that the crown and the visor of this cap aren't the same color. Great starting point. From there, I had a couple different reasons to be able to reasonably assume that this cap was blue and red.
Reason #1 - I own an Albany Senators jacket. It's a royal blue jacket, with red on the chest emblem, along with some red on the collar and sleeve cuffs. It was owned by Leverett “Lev” Spencer, who only played for the Senators in 1959. So that means that just five years after 1954, Senators colors were blue and red.
Reason #2 - This isn't the first reproductions of a 1950s Senators hat. Once upon a time, Ebbets Field Flannels made a 1951 Senators cap. It had a royal blue crown and a red visor. If that's not enough, there were also reproductions of a 1953 Senators ballcap made by New Era. Royal blue crown, red visor. As far as I'm concerned, those 2 things establish that the teams colors were also blue and red before 1954.
I'm not quite sure why they decided to abandon their usual sans serif "A" emblem in favor of this slightly wider serif version, but as far as I know, that was unique to '54. That's all I've got. As usual, let me know if you think I got it wrong and have any kind of supporting evidence! Big thank you to my pal Steve Mann for the photos and info from his Senators collection.