I am bringing in raster (tif) data (ocean pH) into ArcGIS (exported from QGIS). I expected it to come in in a way that I could adjust the colours. However, it is coming in as RGB colour bands (three bands) and I am unable to query the pH values. Is there a different way to bring in the data so I would be able to adjust the colours and query the values?
You have received an image representing your raster data. You need the actual raster data. It sounds like there are several bands on the source raster data. You'll need to ask for an export of the ocean ph band, if that is the info you want.
You will need to go back to the source and ask for an export of the raster data, not just an image export from QGIS.
You will then be able to query the raster data to find the values you are looking for and you will be able to symbolize based on the raster values.