I need to design a letterhead and I have this watercolour effect which I created in Photoshop (RGB file). I want to take this to Illustrator and work with this as part of my design for the letterhead. When I place it in Illustrator, the colours seem to vary quite a bit. I suppose this is because its in CMYK and the original is in RGB. Should I be re-working the original watercolour arwork in CMYK in Photoshop? Would the colours match when I take it to Illustrator?
Should I be re-working the original watercolour arwork in CMYK in Photoshop?
Working in CMYK is not that simple, it needs to take into account the profile.
A basic example is the maximum amount of ink. You should not use for example c100m100y100k100.
Most art work, paintings, are better to be done in RGB and then just converted to CMYK. The colors change yes, but you need to live with the change.(*)
An exception is when you have pure colors, for example a watercolour letterhead with only yellow and magenta to produce and combine a yellow-orange-red paint. In a specific case like that yes, you could work directly in CMYK.
(*) But is important to turn the profile on so you can see on screen the aproximate result in CMYK when working in RGB.