ENH: Matching line colors when doing ODS

[sbtlaarzc]

When doing ODS measurements, the time-domain and frequency-domain plots are a bit confusing due to the missmatching colors.

While the time domain contains a seperate reference and response time series figure, the frequency domain contains both in one figure. The colors are therefore missleading, i. e.: the red curve does in time domain not physically represent the red curve in frequency domain.

[matmr]

I'm on it.