In a double list box in a html form, the buttoms in between the form and the frames are very faint. If a fresh single list box is added the buttons are clearly visible.

Screenshots of the issue:

1) Check if AppStudio has been upgraded from an older release to a later release. If yes, the issue can be fixed by running, "thisfoci.bat" as an Administrator and it will apply the code to switch from the older Double List control arrows to the new double arrow control arrows.

OR

2) Check external CSS that is being used on the HTML page. You can also change the color of the double list arrows by using CSS. 

Use the browsers developer tools to find a common class for the arrows and apply the following CSS:

.IBI_btn-moveOptions {
 color: blue;
 }

This code can be added to the 'Embedded CSS' tab, see below image for reference.

NOTE: Here IBI_btn-moveOptions is the class applied on the arrow button. Hex color codes can also be used.