That worked out pretty well, in general. For the small components, the trick was to find a web site that can transform from rgb-base 10 to rgb-base 16 to HSL, then one has to offset that result to Gimp's offset HSL to colorize the component.
There is one anomaly, however, in the larger structure. While most places where the new blue is expected are presented as that color, tagging files or folders in Nemo yields a much darker blue color, almost black. This is also true of tagging text in gedit. I thought that perhaps somewhere a high factor shade command was in play, but couldn't find it among the style sheets and rc files. Mint-X produces a reasonable green for these two actions, and Mint-X-Blue yields a bright blue. I have scrutinized the changes and see no errors in color replacment for "NeuBlue", which is a rather modest color shift. (398ee7 --> 3a6ea5)
I would appreciate any clues to where Nemo and gedit take their color from. GNOME.org has a lot of documentation, but nothing I found that would answer "this color comes from here."
Desktop 1: DFI Lanparty UT nF4 SLI-D/AMD Athlon 64 San Diego 2.2 GHz/G.SKILL 1GB x 2 DDR 3200/BFG GeForce 7800 GT/Ubuntu10.04
Desktop 2: Gigabyte 770T-USB3/AMD Phenom II X4 965 3.4 GHz/2GB x 2 + 4GB X 2 DDR3 1333/EVGA GeForce 9800 GT/Mint 17.1 MATE