Grass seed grown but pale

Hello,

I recently showed some grass seed in a few patchy areas. It’s grown really well all over, except in one area it’s come up much paler in colour. It looked ok before I cut it (first cut yesterday at about 10cm length) but since cutting the pale really stands out. 

Does anyone one have anybody ideas how I could make it blend in, or what I may have done wrong?

Thanks in advance

Jason