This doesn't happen in the "real" arduino IDE but this simple program ....

#include <Arduino.h>

class Color {
public:
	Color() {}
	Color(int ri) { setColors(ri); }
	Color *  setColors(int ri) {
		r = ri;
		return this;
	}
	int r = 0;
};

void dosomething(Color * c) {
	Color * d = c;
	int r = d->r;
	Serial.println(r);
}

Color c(666);

void setup() { 	Serial.begin(115200); }

void loop() {
	dosomething(c.setColors(999));
	delay(1000);
} 

.... complains ("...not declared in this scope") about the Color references.

Extra weirdlyer, if I simply move the Color class definition to a header file and include it, it compiles & runs fine.

OK!.... Thanks for the fast response!!!

But its still weird.

I looked at your code again and see that Visual Studio gives some false intellisense errors with a class defined along side normal code.

To be honest it is cleaner and better to user .h files.

I moved you Color class to a Color.h file which I added to the project. 

To create the Color.h file, right click the project and select "Add New Item"

In Color.h I have this code:-

// Color.h

#ifndef _COLOR_h
#define _COLOR_h

#include "arduino.h"

class Color {
public:
	Color() {}
	Color(int ri) { setColors(ri); }
	Color *  setColors(int ri) {
		r = ri;
		return this;
	}
	int r = 0;
};


#endif 

Then your .ino code becomes more manageable and simpler:-

#include "Color.h"

Color c(666);

void dosomething(Color * c) {
	Color * d = c;
	int r = d->r;
	Serial.println(r);
}


void setup() { Serial.begin(115200); }



void loop() {
	dosomething(c.setColors(999));
	delay(1000);
}