The phrase "ability to blend in" is correct and usable in written English.
You can use it when discussing someone's skill or capacity to adapt to different environments or social situations without drawing attention.
Example: "Her ability to blend in at social gatherings made her a valuable asset to the team."
Alternatives: "skill to assimilate" or "talent for fitting in."
In these highly charged social situations, where the focus of attention is on you, the greatest skill you need is the ability to blend in quickly.
All staff are chosen for their ability to blend in.
Their campaign has been helped by their ability to blend in with ordinary villagers, using traditional loyalties or brute force to get support and assistance.
She is stealthy, with an ability to blend in with the leaves, and has the habit of creeping up on humans so they catch a glimpse of her in their rear view mirrors moments before she strikes.
One reason Luck said he felt comfortable returning to college this year despite the likelihood that he would have been the top pick in the 2011 N.F.L. draft was his ability to blend in among the other students at Stanford.
Sato has made up for the numbers difference in numbers with experience, intelligence and a unique ability to blend in on a team that includes Foyt, the feisty Texan; his adopted son, Larry, the calming team director; the veteran engineer Don Halliday; and, this month, the rookie Conor Daly, 21.
Osborne notes their ability to blend into a society that barely notices them.
Saunders's sonic palette is not new — composers such as Helmut Lachenmann and Salvatore Sciarrino have used some version of it for decades — but she has a virtuosic ability to blend colors in fresh ways.
Leyland's genius rests in his ability to blend the persona of a man born in the hardscrabble Ohio rust belt during World War II with an approach that earns the respect of players who were not even born when he first managed in the majors.
In fact, though, the greater similarity lies in their ability to blend a lyrical prose – the prose of longing, missed connections, grasped pleasures – with an almost uncanny depth of observation.
Not just in its casual and apparently effortless excellence, but in its ability to blend entertainment and insight, comedy and poignancy, even drama and reality, things that are difficult by themselves but a whole lot harder in combination.
