Hi. I'm new to this forum also. I saw you hadn't gotten any replies and wanted to offer a couple thoughts.
First, lighting is a
really broad topic.
As you noted, the first thing you need to figure out is what type of light fixture you have. Hopefully you can find some details on the fixture, and you can often find details on the bulb as well. If not, you could take a bulb with you to the home supply and have someone help you track down the type of bulb you have. Knowing that will make a huge difference in your replacement options.
Once people know what type of bulb you are dealing with, it will be much easier to offer suggestions.
Second, knowing what you want the bulb to accomplish--in your case, highlight fish coloration--will help focus your choices even more.
Last, but not least, even knowing the type of bulb and your end goal, you will likely have multiple options. And at this point, things get fairly subjective and a lot will come down to personal preference. As they say, YMMV. A bulb that makes one person happy--with their substrate, background, decorations and fish--may not provide the exact same results in your tank.
p.s. I also think it would be easier for people who know lots about lighting to find you and help you, if you mentioned lighting in your post topic.