Most exhibit green/blue casts which is expected. So I need an efficient workflow to get these into a usable condition. A few may be worth manual edits, but not many, given the quantity. Is a 'colour profile' what I need?
Whether a profile is the right answer can depend on where the casts are coming from. A profile is the most useful when the color casts are coming from the device, like if the scanner itself is not rendering balanced colors. A profile can also be useful for very common overall casts, such as daylight slide film exposed indoor lighting.
But Lightroom has other ways to address corrections for bulk scans, and you should consider those in case they are better for the job at hand. The Profiles feature was already mentioned, but you might not have to go that far. If the color cast can be easily fixed with the Develop module controls, use the quicker Presets feature instead. Fix one slide scan, and save those settings using the Preset panel on the left side of the Develop module. Then select any number of scans that need the same correction, and apply the preset, and you've instantly corrected multiple scans. The nice thing about presets is that it's fast and easy to create any number of variations of them as color casts shift across different rolls or ranges of frames.
That last sentence, by the way, should help you figure out which solution you should use. If the color cast is the same no matter what roll of slides you scan, then maybe you need a profile for the scanner. But if the color cast varies with the roll, film type, or even within the same roll, a profile can't fix all those variations and you should try making Presets as needed for each case. Or, if the cast is especially challenging, spend a little more time making a User Profile (not a formal scanner profile) as I-See-Light described. So be aware that you have all those options: Presets and User Profiles as well as a scanner profile.
Also pay close attention to what kind of cast you are looking at. If it's completely uniform, it could just be a simple white balance adjustment. But if the cast is different in the highlights and shadows, then you are looking at an adjustment using individual RGB tone curves or Split Toning. And if the cast actually changes across a slide, like increasingly blue toward the edges, now you're looking at applying a gradient local adjustment correction. All of those are Develop settings that can be saved as part of a preset and applied to scans in bulk to save time.
