Wait. I just looked at what Xkit calls "old blue".
The hex for that is #36465d. It's darker, but that is to be expected because the poll restricted the possible values to only the color space where the sum of all 3 colors adds up to 255, so that removes a variable. You expect the saturation and value to be different just because of that - the saturation and value are 42% and 36% respectively for Tumblr Blue, while for this color they're 49% and 45%. It's a bit lighter blue, with a tiiiiny bit more saturation.
If you just look at the hue angle, however, that's completely unconstrained.
The hue angle for Tumblr Blue is 215°.
The hue angle for this color is...
You didn't just make "Tumblr Blue"
You made pretty much as close as this poll could've POSSIBLY GOTTEN to the actual fucking Xkit-defined "Tumblr Blue".
(for the record, if you wanted to truly get Tumblr Blue with this poll, the actual closest you could've gotten would've been 25% red, 32% green, 43% blue)