diff --git a/tests/alpha-blending-test.c b/tests/alpha-blending-test.c
index e2916be9..b3f8bdee 100644
--- a/tests/alpha-blending-test.c
+++ b/tests/alpha-blending-test.c
@@ -299,7 +299,7 @@ check_blend_pattern(struct buffer *bg, struct buffer *fg, struct buffer *shot,
 	uint32_t *bg_row = get_middle_row(bg);
 	uint32_t *fg_row = get_middle_row(fg);
 	uint32_t *shot_row = get_middle_row(shot);
-	struct color_float max_diff = { 0.0f, 0.0f, 0.0f, 0.0f };
+	struct color_float max_diff = { .rgb = { 0.0f, 0.0f, 0.0f } };
 	bool ret = true;
 	int x;
 
diff --git a/tests/color-shaper-matrix-test.c b/tests/color-shaper-matrix-test.c
index 0c04e070..331336a3 100644
--- a/tests/color-shaper-matrix-test.c
+++ b/tests/color-shaper-matrix-test.c
@@ -193,7 +193,7 @@ gen_ramp_rgb(const struct image_header *header, int bitwidth, int width_bar)
 		hue_index = MIN(hue_index, num_hues - 1);
 
 		for (x = 0; x < header->width; x++) {
-			struct color_float rgb = { 0, 0, 0 };
+			struct color_float rgb = { .rgb = { 0, 0, 0 } };
 
 			value = (float)x / (float)(header->width - 1);
 
@@ -360,7 +360,7 @@ process_pipeline_comparison(const struct image_header *src,
 			    const struct setup_args * arg)
 {
 	const float max_pixel_value = 255.0;
-	struct color_float max_diff_pipeline = { 0.0f, 0.0f, 0.0f, 0.0f };
+	struct color_float max_diff_pipeline = { .rgb = { 0.0f, 0.0f, 0.0f } };
 	float max_allow_diff = arg->pipeline.tolerance / max_pixel_value;
 	float max_err = 0;
 	float f_max_err = 0;
diff --git a/tests/color_util.c b/tests/color_util.c
index 511b8d9e..bc5ca801 100644
--- a/tests/color_util.c
+++ b/tests/color_util.c
@@ -29,8 +29,18 @@
 #include <assert.h>
 #include <stdlib.h>
 #include <string.h>
+#include <stddef.h>
 #include "shared/helpers.h"
 
+static_assert(sizeof(struct color_float) == 4 * sizeof(float),
+	      "unexpected padding in struct color_float");
+static_assert(offsetof(struct color_float, r) == offsetof(struct color_float, rgb[COLOR_CHAN_R]),
+	      "unexpected offset for struct color_float::r");
+static_assert(offsetof(struct color_float, g) == offsetof(struct color_float, rgb[COLOR_CHAN_G]),
+	      "unexpected offset for struct color_float::g");
+static_assert(offsetof(struct color_float, b) == offsetof(struct color_float, rgb[COLOR_CHAN_B]),
+	      "unexpected offset for struct color_float::b");
+
 struct color_tone_curve {
 	enum transfer_fn fn;
 	enum transfer_fn inv_fn;
@@ -154,9 +164,10 @@ Power2_4_EOTF_inv(float o)
 void
 sRGB_linearize(struct color_float *cf)
 {
-	cf->r = sRGB_EOTF(cf->r);
-	cf->g = sRGB_EOTF(cf->g);
-	cf->b = sRGB_EOTF(cf->b);
+	int i;
+
+	for (i = 0; i < COLOR_CHAN_NUM; i++)
+		cf->rgb[i] = sRGB_EOTF(cf->rgb[i]);
 }
 
 static float
@@ -191,9 +202,10 @@ apply_tone_curve(enum transfer_fn fn, float r)
 void
 sRGB_delinearize(struct color_float *cf)
 {
-	cf->r = sRGB_EOTF_inv(cf->r);
-	cf->g = sRGB_EOTF_inv(cf->g);
-	cf->b = sRGB_EOTF_inv(cf->b);
+	int i;
+
+	for (i = 0; i < COLOR_CHAN_NUM; i++)
+		cf->rgb[i] = sRGB_EOTF_inv(cf->rgb[i]);
 }
 
 struct color_float
diff --git a/tests/color_util.h b/tests/color_util.h
index 96f50049..f822d00a 100644
--- a/tests/color_util.h
+++ b/tests/color_util.h
@@ -27,8 +27,21 @@
 #include <stdint.h>
 #include <stdbool.h>
 
+enum color_chan_index {
+	COLOR_CHAN_R = 0,
+	COLOR_CHAN_G,
+	COLOR_CHAN_B,
+	COLOR_CHAN_NUM
+};
+
 struct color_float {
-	float r, g, b, a;
+	union {
+		float rgb[COLOR_CHAN_NUM];
+		struct {
+			float r, g, b;
+		};
+	};
+	float a;
 };
 
 struct lcmsVEC3 {