For a hover effect on a button that uses #263EDB (Rich Blue), you’ll want to choose a lighter or slightly different shade that still complements the original color while providing a noticeable change. Here are a few options:

1. Lighter Blue: Use a lighter version of #263EDB , such as #4A6EDB . This will keep the same tone but will be light enough to indicate that the button is interactive.

2. Sky Blue: #4CA1E0 is a soft sky blue that would provide a fresh and engaging hover effect, creating a nice contrast with the rich blue.

3. Cyan: A vibrant shade like #00A6E0 would also work well, giving a lively and inviting feel when users hover over the button.

4. Bright Blue: You could also use #3A8EDD , which is slightly brighter and adds a bit of energy to the interaction.

Any of these colors would work well for a hover effect, enhancing user experience by indicating interactivity. Would you like to see how these hover effects might look in a design mockup, or do you need assistance with anything else?