Use of multiple signals of distinct centre frequency transmitted from the same GNSS satellite allows direct observation and removal of the ionospheric delay. With signals available on multiple GNSS frequencies, multi-frequency correction schemes can be applied to eliminate the influence of the ionosphere from the measurements by exploiting the expected dispersive effects introduced by propagation through the ionosphere. While the general assumption of nearly perfect correlation between the effect measured on multiple independent signals is correct in normal conditions, detailed knowledge of scintillation effect correlation between the GNSS frequency pairs is desirable in order to quantify the potential transient errors due to any de-correlation of the effect, as this error de-correlation will dictate the extent to which frequency diversity may be applied to mitigate the scintillation impact on the GNSS measurement accuracy. Several studies investigating the scintillation effect on correlation across GNSS frequencies are already available, however these studies focus mainly on characterizing the correlation of amplitude scintillation by means of simulated data, or the projection of signal fluctuations observed on GPS L1 on to new frequencies. This article describes phase scintillation correlation analysis based on phase scintillation observations recorded at high latitude regions of Norway on multi frequency enabled satellites (GLONASS L1/L2), and at equatorial latitudes recorded via measurements to triple frequency enabled satellites (GPS L1/L2/L5). The obtained results indicate that for all frequency pairs considered in the analysis, when phase scintillation alone is present, a higher intensity of phase scintillation produces an increasing level of correlation, but results in a slightly higher absolute level of measurement residual, however when amplitude scintillation is present the correlation relationship between the carriers can become temporarily inverted resulting in relatively large transient errors leaking through ionosphere free combinations.