Mareike,
This sounds like something that you should post over on the
Keyshot forum.
There are quite a few more seasoned users of Keyshot there and may have already run into this issue.
(Edit)
After thinking about this for a while I figured that this isn't the first time someone needed to come up with a custom color. So I did some poking around to see if there were some online tools that could help in your search to mix the RAL colors. What I found was a
Combine Color Tool. But to use it you need a
RGB to HEX converter to convert the RGB values of the RAL colors.
I also came across a
RGB Color Gradient maker but it doesn't allow a percentage of one color over the other, as in your request.
This
Online color mixing tool shows promise. It lets you define a custom palette with the two RAL colors to combine and vary the amount by "adding" more of one or the other color. It does not allow for your mix of 100% of RAL6003 and 30% of RAL6007. The closest I was able to get was a 67% to 33% mix shown in the attached image. One issue is that it changed the Hex value slightly from the converted RGB values.
(Edit)
I dug into this and found that I was using the RAL 841 colors in Keyshot. It appears the online converters used the RAL 840 colors and would not accept the color numbers for RAL 841.
Another thing you might try is, and this may be a long shot, if you have a physical sample that you could take a picture of and load that into your computer. Then use the Eye dropper tool to pick the color off the picture.
