Yes it can be normal behaviour. Have you sexed the gouramis? The males have longer and pointier dorsal and anal fins than the females whose fins are more rounded. Gouramis are gouramis, whether they are opaline, 3 spot or whatever so they will not differentiate between colour types. It is possible you have 2 males and they are fighting it out for the top position, or you have a pair and the male is showing off. Keep an eye out for any damage caused or signs the less dominant fish is getting stressed.