The following changes (performed in the GIMP) were used to create the *-relax-blue.png versions of the oxygen icons:

Original colour     Master hue 
Green               97
Yellow              ?

Original colour     Green   Yellow
Master hue          97      180
Y hue               .       .
Y lightness         .       -44
Y saturation        .       -36
R hue               .       .
R lightness         .       -44
R saturation        .       100


For the roll.png icons, the image was transformed to RGB, the colours inverted, and colour balance midtones set to:
    Cyan - Red = -100
    Magenta - Green = 10
    Yellow - Blue = 100
The colour balance highlights were set to:
    Cyan - Red = -100
    Magenta - Green = 0
    Yellow - Blue = 100
