Color: Fix method return types to this

[eunjiyun]

Summary

Fix Color method return types from Color to this for correct subclass chaining.

Evidence

JS implementation:

• three.js/src/math/Color.js:187–525 — setScalar, setHex, setRGB, setHSL, setStyle, setColorName, copySRGBToLinear, copyLinearToSRGB, convertSRGBToLinear, convertLinearToSRGB all end with return this

Declaration:

• types/three/src/math/Color.d.ts:233–298 — all of the above are declared as returning Color instead of this

Observed mismatch:

• Return type is declared as Color, but the JS implementation returns this.
• Declaring Color instead of this loses the subclass type when chaining. For example, if a user extends Color and chains one of these methods, TypeScript narrows the type to Color, making subclass-specific methods inaccessible:

  const exampleColor = new Color4(1, 0, 0, 0.5);

  exampleColor.a = 0.8;                    // direct access works
  exampleColor.setRGB(1, 1, 1).a = 0.8;    // Property 'a' does not exist on type 'Color'
                                 //    (setRGB is declared to return Color, not `this`)

• Other methods in the same file (set, copy, add, lerp, etc.) already correctly use this. These methods were simply missed.

Local Check

​bash pnpm test # failed: unrelated ESLint plugin error ​

Scope

• Declaration file only
• No runtime change
• All changes isolated to Color.d.ts