David Tweed:

>Basically, whether a given colour means the same power wherever it is in the plot?

I do not use Log, Mathematica's scalograms are by default in Log/Octave scales. I dislike that, so I wrote a converter to get rid of the log so I could report periodicity with the exact values, here is the code I use:

period = 1/(cwd[
"SampleRate"]/(#*
cwd["Wavelet"]["FourierFactor"])) & /@ (Thread[{Range[
cwd["Octaves"]], 1}] /. cwd["Scales"]);
ticks = Transpose[{Range[Length[period]], period}];