[raymo]

I don't know what ISO or aperture settings you used, but with almost any conceivable setting 2 minute subs will show colour. My very recent images
of the LMC posted here show plenty of colour with 45 sec subs.
I assume that you stacked your subs in DSS; if so, are you familiar with DSS or are you new to it. Also, did you do any processing in DSS, or use other software such as Photoshop or Pixinsight. In case you are not aware of it,
DSS only stacks the subs and delivers a near mono final image; it is then up to you to balance the colours until the RGB cones align with each other to form a single cone, and all three cones need to be moved left to darken the sky background, but not too far, or precious detail will be lost. Also the colour saturation needs to be set at a starting point of 17, and adjust to taste from there. Your Sony is better at picking up red, so you will quite likely see some red, which my Canon can't pick up.
If you put the final stacked image into other software for processing, then
I can't help you. Anyway, the colour is genuine, not introduced, and you don't need more time, just need to bring out the colour during processing.
raymo