Platies (trio), swordtails (trio), mollies (trio), guppies (trio), golden gourami (stick to just one), fire rasbora (6 at elast), golden barbs (6 minnimum), tiger barbs (at elast 7 - they are nippy), schuberti barbs (6 minnimum), rummynose tetras (6 at least), golden-eyed dwarf cichlid (depending on what else is in the tank), gold rams (pair - whether you should keep them depends on set-up), certain angelfish varieties (pair and not with very small fish), bettas (a single male, not with anything nippy or with gouramies/guppies OR at least 4 females, again, watch the tankmates), thick-lipped gourami (depending on tankmates - either a single one, if male, a pair or a trio if it'll be the only species of gourami), honey gouramies (some are mroe yellow than others

- a trio would be good but not with aggressive gouramies/tankmates), skunk loach (can be very aggressive, don't keep with timid fish or with any particularly peaceful bottom dwellers - eg: cories), some bronze cory color morphs (a group of 4 at elast), golden zebra loaches (small group), zebra loaches (quite boisterous), several species of rainbowfish (group of 6 minnimum - avoid the very large ones) and there's many more.
Your best bet would be to give us a hint as to what their tankmates will be.
Also, what I've suggested above won't all go together. Research whatever you are interested in thoroughly BEFORE you buy it and add it to your tank. They aren't all completely yellow either but the vast majority are or are predominantly bright yellow - with some, only a color morph of the species is yellow; eg: guppies.