If your looking into cichlids and want color your best bet would be Malawi. If you choose Malawi do your research well Some are more aggressive then others. Yellow labs or peacocks are very colorful and less aggressive. Tanganikan cichlids are great also but you will not find the brighter colors. They do however IMO have more personality. Here is a link maybe it will help. I can't stress this enough if you wish to keep cichlids make sure you do your research first. Find, decide which species you want if more than one type make sure they have the same water params and needs.
Cichlids can be tricky to care for but only IF you do not do your research we have two tanks with cichlids one Tanganikan and one Malawi they are great fish to have much personality and great to watch but they do require a much different enviroment than your typical tropicals.
You can also find tropical on the site as well read about everything and then decide which way to go.
Tropical fish although are great fish to keep also. At 150 gallons you have the chance to have a great planted tank with many varieties of fish. Examples.. A shoal of Cardinal tetras would be beautiful there are many types of tetras you could go with. Rainbow fish are also very nice. Corys would make a nice addition as well. Personaly haveing 4 children of my own they tend to like the tropicals more my daughter has a 10gallon of her own. She loves the little shrimp and her tetra with a few zebra danios.
Best of luck