With the System 7.5 Color Picker installed on color systems, you will see a 'More Choices' button in the ClarisImpact Color Editing window.
When you click More Choices button, there are two choices: Apple HSL and Apple RGB. Clicking on Apple RGB will give you a window where you can adjust the Red, Green and Blue with a slider or by typing in the percentage desired.
Pre�?System 7.5 systems had one window with the RGB
controls on the left side of the window. With those limited controls, you could only type in the number or click on the arrows to change the Red, Green, and Blue.