You are probably right, it is an issue with color profiles and gamut. Aperture does use a different raw converter, which will create some variance. In fact, many like the look of straight Aperture raw conversions over straight ACR conversions. But if the washed out look is dramatic, and Photoshop opens your raw files okay, then it must be a profile issue.
It may help to explain how you are exporting from Aperture. Are your source files raw files, PSDs, TIFFs, or JPEGs? Are you exporting masters, or are you exporting versions? If you're exporting versions, take a look at your "source preset" when exporting. What color profile are you embedding?
Although if you are embedding any color profile, Photoshop and Lightroom should pick it up.
All I've read is that Lightroom manages profiles more transparently than Photoshop, but perhaps someone could jump in here and say how it is managed.
Finally, what purpose are you exporting and importing into Lightroom? If you're migrating your library to a Lightroom catalog, you may be best served by using the Aperture migration plug-in.
The plug-in still has issues with foreign characters, importing all previews, and face keywording and keywording previews. You'll be better off waiting until these issues are fixed. Even if you can't, the plug-in would still be a better option than a manual attempt, unless you're doing something other than migrating your Aperture library.
Thank you so much for your response.
It was in the export setting for Tiff images that i had created a while ago. This was assigned an sRGB profile that was causing the changes to in colour to occur.
When i export Tiffs from Aperture with the Pro RGB profile. Most images are showing correctly. But i get some that are washed out. When i open in Photoshop (Creative Cloud version) and select the 'With Lightroom adjustments it is still washed out. but when i 'open original' it opens with the correct colour. I have rebuild 1:1 previews and tried so many different options to try to figure it out but not having any luck. How does Lightroom build previews and is there a way to change this. Also tried on different computers.....
ProPhoto tends to wash out when read by an application that does not apply color profiles, or defaults to sRGB. For example, if you open a ProPhoto image in Preview, color management is applied. If you browse the image in finder, both the thumbnail and quick preview don't apply the profile.
Sounds like the same is happening here. Perhaps others can step in, I'm new to Lightroom, and don't yet know how Lightroom uses color profiles.