Well, you may need to change the default color palette to use the custom color which is not the part of Excel 2003 default color palette (Amber (RGB- 255, 191,0)). If you set a color which is not in the palette, it will not take effect. Please see the following documentation links for Default Color Palette and how to add the custom colors in the Palette,
For .NET
Also, following documentation link provides the code samples and details regarding how to apply the background color and patterns,
For Java
Also, following documentation link provides the code samples and details regarding how to apply the background color and patterns,