I'm repeating a particular background image on each page of a calendar and would like to change its colors on each page. There are 2 gradients in the image which use a total of four different colors. I'm not at all skilled in color theory and was wondering if anyone can please tell me if there's an easy way to come up with harmonious color combinations that I can apply to the original Illustrator file? My shortcut solution would be to convert the color to grayscale and apply a color overlay, but the image just looks flat when I do that. I would prefer to adjust the gradients individually but just don't know how to find compatible colors.
Here's a preview of the image followed by a DropBox link to the Illustrator file.
Couple ideas for you:
First, try using the color wheel on color.adobe.com. Select the middle color and add your hex code to the color. The app will automatically show you analogous colors. See an example here. You can also experiment with the other color rules in the Color Rule menu (just click on one of them).
Second, take a look at themes created by others. If you are looking generally for colors that work well with yellow, you can browse the most popular themes and spot some which use yellow.
I hope that helps.