Is it correct to say '较出色‘? Is '做得较出色‘ good Chinese? 

Seems to me that it means that something is outstanding, remarkable, or it is not, in which case it is commonplace. I suppose this begs the question 'Where does remarkable begin?'
(Someone)做(something)做得较出色 is perfect Chinese.
较出色 can be translated into relatively outstanding 

I think Chinese tend to be modest when compliment someone related to them. So it is common to hear the boss praises his subordinate 做得较出色 or a mother praises her son 做得较出色 in front of a third party.

It is perfectly fine if you remove the "较" which as user3306356 pointed out "It's more formal (较 vs. 比较). 较 means relatively or comparatively". 

P.S. if you hear 较出色, someone/something probably is pretty outstanding.